Item 1. Reports to Stockholders.

(a)

Table of Contents

PERFORMANCE as of June 30, 2026

​(1)    The Fund commenced operations on July 2, 2018.

​(2)    Performance returns are net of management fees and other Fund expenses.

​(3)    The return shown is based on net asset value (“NAV”) calculated for shareholder transactions and may differ from the return shown in the Financial Highlights, which reflects adjustments made to the NAV in accordance with accounting principles generally accepted in the United States of America.

​(4)    The Standard & Poor’s 500 Index (“S&P 500 Index”) is a capitalization-weighted index, representing the aggregate market value of the common equity of 500 large-capitalization stocks primarily traded on the New York Stock Exchange.

​(5)    The Bloomberg US Corporate High Yield Bond Index measures the USD-denominated, high yield, fixed-rate corporate bond market.

​(6)    The Morningstar LSTA US Leveraged Loan Index is a market value weighted index designed to capture the performance of the US leveraged loan market.

Performance data quoted represents past performance, which is not a guarantee of future results. Current performance may be lower or higher than the performance quoted. The principal value and investment return of an investment will fluctuate so that your shares, if repurchased by the Fund, may be worth more or less than their original cost. Total return measures net investment income and capital gain or loss from portfolio investments. All performance shown assumes reinvestment of dividends and capital gains distributions.

The Fund is a continuously offered, non-diversified, closed-end management investment company that is operated as an interval fund. The Fund is suitable only for investors who can bear the risks associated with the Fund’s limited liquidity and should be viewed as a long-term investment. The Fund’s shares have no history of public trading, nor is it intended that its shares will be listed on a national securities exchange at this time, if ever. Investing in the Fund’s shares may be speculative and involves a high degree of risk, including the risks associated with leverage. Investing in the Fund involves risk, including the risk that shareholders may receive little or no return on their investment or that shareholders may lose part or all of their investment. The Fund intends to invest primarily in the equity and, to a lesser extent, in the junior debt tranches of collateralized loan obligations (“CLOs”) and other similarly structured vehicles that own or have exposure to a pool of senior secured loans made to companies whose debt is rated below investment grade or, in limited circumstances, unrated. The Fund’s investments in the equity and junior debt tranches of CLOs are exposed to leveraged credit risk. Investments in the lowest tranches bear the highest level

of risk. The Fund may pay distributions in significant part from sources that may not be available in the future and that are unrelated to its performance, such as a return of capital or borrowings. The amount of distributions that the Fund may pay, if any, is uncertain.

ASSET ALLOCATION as of June 30, 2026*

*      Holdings are subject to change.

        Percentages are based on net assets of the Fund.

TOP TEN HOLDINGS* as of June 30, 2026

*      Holdings are subject to change and exclude cash equivalents.

GROWTH OF A HYPOTHETICAL $10,000 INVESTMENT

The graph below illustrates the growth of a hypothetical $10,000 investment assuming the purchase of common shares at the NAV of $20.00 on July 2, 2018 (commencement of operations) and tracking its progress through June 30, 2026.

The hypothetical $10,000 investment at inception includes changes due to share price and reinvestment of dividends and capital gains. The chart does not imply future performance. Indexes are unmanaged, do not incur fees, expenses or taxes, and cannot be invested in directly. Performance quoted does not include a deduction for taxes that a shareholder would pay on the repurchase of its shares by the Fund.

(a)   The level 3 assets were a result of unavailable quoted prices from an active market or the unavailability of other significant observable inputs.

(b)   Collateralized loan obligations (“CLO”) equity positions are entitled to recurring distributions which are generally equal to the remaining cash flow of payments made by underlying securities less contractual payments to debt holders and CLO expenses. The effective yield is estimated based upon the current projection of the amount and timing of these recurring distributions in addition to

the estimated amount of terminal principal payment. Effective yields for the CLO equity positions are updated generally once a quarter or in connection with a transaction such as an add-on purchase, refinancing or reset. The estimated yield and investment cost may ultimately not be realized. Total fair value of the securities is $343,609,277, which represents 93.60% of net assets as of June 30, 2026.

(c)    Securities are exempt from registration under the Securities Act of 1933 and are deemed to be “restricted” securities. As of June 30, 2026, the total fair value of these securities amounts to $404,111,120, which represents 110.08% of net assets.

(d)   Positions represent investments in a warehouse facility, which is a financing structure intended to aggregate loans that may be used to form the basis of a CLO position.

(e)    Variable rate security. Interest rate resets periodically. The rate shown is the effective interest rate as of June 30, 2026. For securities based on a published reference rate and spread, the reference rate and spread (in basis points) are indicated parenthetically. Certain variable rate securities are not based on a published reference rate and spread but are determined by the issuer or agent and are based on current market conditions. These securities, therefore, do not indicate a reference rate and spread.

(f)    Purchase of this security was settled after June 30, 2026.

(g)   Equity tranches in securitizations of limited partnership interests in a loan fund (“Feeder Fund Investments — Equity”) are entitled to recurring distributions, which are generally equal to the remaining cash flow of payments made by the underlying loan fund less contractual payments to debt holders and fund expenses. The effective yield is estimated based upon the current projections of the amount and timing of these recurring distributions in addition to the estimated amount of the terminal principal payment. Effective yields are generally updated once a quarter or in connection with events such as an add-on purchase, refinancing or reset. The estimated yield and investment cost may ultimately not be realized. As of June 30, 2026, the total fair value of Feeder Fund Investments — Equity was $36,400,000, representing 9.92% of net assets.

(h)   Debt tranches in securitizations of limited partnership interests in a loan fund (“Feeder Fund Investments — Debt”) are entitled to contractual interest payments derived from the cash flows generated by the underlying loan fund. As of June 30, 2026, the total fair value of Feeder Fund Investments — Debt was $498,000, representing 0.14% of net assets.

(i)    SonicWall was a loan held within a CLO warehouse managed by Fortress, in which the Fund held an equity interest. Upon the conversion of the warehouse into FCO 2026-27A, the loan was identified as ineligible for inclusion in the CLO’s collateral pool. Although the loan remains held within the CLO structure, the economic interests in the loan were retained by Flat Rock Opportunity Fund and the other equity investors in the original warehouse entity, rather than being included in the FCO 2026-27A waterfall.

(j)    Rate disclosed is the seven-day effective yield as of June 30, 2026.

Investment Abbreviations:

SOFR - Secured Overnight Financing Rate

Reference Rates: 
3M US SOFR - 3 Month SOFR as of June 30, 2026 was 3.73%.

​(a)    $10,000 liquidation value per share. 4,500 shares authorized, issued and outstanding.

Flat Rock Opportunity Fund (the “Fund”) is registered under the Investment Company Act of 1940, as amended, (the “1940 Act”) as a non-diversified, closed-end management investment company. The shares of beneficial interest of the Fund (the “Shares”) are continuously offered under Rule 415 under the Securities Act of 1933, as amended (the “Securities Act”). The Fund operates as an interval fund pursuant to Rule 23c-3 under the 1940 Act and has adopted a fundamental policy to conduct quarterly repurchase offers at net asset value (“NAV”).

The Fund’s investment objective is to generate current income and, as a secondary objective, long- term capital appreciation.

The Fund was formed as a Delaware statutory trust on February 12, 2018, and operates pursuant to a Second Amended and Restated Agreement and Declaration of Trust governed by and interpreted in accordance with the laws of the State of Delaware. The Fund had no operations from that date to July 2, 2018, other than those related to organizational matters and the registration of its Shares under applicable securities laws.

The Fund has adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update 2023-07, Segment Reporting (Topic 280) — Improvements to Reportable Segment Disclosures. Adoption of the standard impacted financial statement disclosures only and did not affect the Fund’s financial position or the results of its operations. An operating segment is defined in Topic 280 as a component of a public entity that engages in business activities from which it may recognize revenues and incur expenses, has operating results that are regularly reviewed by the public entity’s chief operating decision maker (“CODM”) to make decisions about resources to be allocated to the segment and assess its performance, and has discrete financial information available. The CODM is the President and Chief Executive Officer of the Fund. The Fund operates as a single operating segment. The Fund’s income, expenses, assets, changes in net assets resulting from operations and performance are regularly monitored and assessed as a whole by the CODM responsible for oversight functions of the Fund, using the information presented in the financial statements and financial highlights.

The following is a summary of significant accounting policies followed by the Fund in preparation of its financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The Fund is an investment company under U.S. GAAP and follows the investment company accounting and reporting guidance of the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 946.

Use of Estimates: The preparation of the financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of increases and decreases in net assets from operations during the period. Actual results could differ from these estimates.

Preferred Shares: In accordance with ASC 480-10-25, the Fund’s mandatorily redeemable preferred stock has been classified as debt on the Statement of Assets and Liabilities. Refer to “Note 9. Mandatorily Redeemable Preferred Stock” for further details.

Security Valuation: The Fund determines the NAV of its Shares daily as of the close of regular trading (normally, 4:00 p.m., Eastern time) on each day that the New York Stock Exchange (“NYSE”) is open for business.

The 1940 Act requires the Fund to determine the value of its portfolio securities using market quotations when “readily available,” and when market quotations are not readily available, portfolio securities must be valued at fair value, as determined in good faith by the Fund’s board of trustees (the “Board”). As stated in Rule 2a-5 under the 1940 Act (“Rule 2a-5”), determining fair value in good faith requires (i) assessment and management of risks, (ii) establishment of fair value methodologies, (iii) testing of fair value methodologies, and (iv) evaluation of pricing services. Under Rule 2a-5, a fund’s board may designate the fund’s adviser as “valuation designee” to perform fair value determinations. The Board, including a majority of the members of the Board (the “Trustees”) who are not “interested persons” of the Fund, as such term is defined in the 1940 Act, has designated Flat Rock Global, LLC (the “Adviser”) to perform fair value determinations and act as “valuation designee” for the Fund’s investments.

The Fund records its investments at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The valuation techniques used to determine fair value are further discussed below.

It is the policy of the Fund to value its portfolio securities using market quotations when readily available. For purposes of this policy, a market quotation is readily available only when that quotation is a quoted price (unadjusted) in active markets for identical investments that the Fund can access at the measurement date, provided that a quotation will not be readily available if it is not reliable. If market quotations are not readily available, securities or other assets will be valued at their fair market value as determined using the valuation methodologies approved by the Board.

Equity securities for which market quotations are available are generally valued at the last sale price or official closing price on the primary market or exchange on which they trade.

Short-term debt securities having a remaining maturity of 60 days or less when purchased are valued at cost adjusted for amortization of premiums and accretion of discounts, which approximates fair value.

The Fund primarily invests in the equity or junior debt tranches of collateralized loan obligations (“CLOs”). In valuing such investments, the Adviser considers a number of factors, including: 1) the indicative prices provided by a recognized, independent third-party industry pricing service, and the implied yield of such prices; 2) recent trading prices for specific investments; 3) recent purchases and sales known to the Adviser in similar securities; 4) the indicative prices for specific investments and similar securities provided by the broker who arranges transactions in such CLOs; and 5) the Adviser’s own models, which will incorporate inputs that may include, but not limited to, assumptions for future loan default rates, recovery rates, prepayment rates, and discount rates — all of which are determined by considering: a) observable and third-party market data; b) assumptions related to the underlying assets in the CLO that are provided by the Underlying Manager; and c) prevailing general market assumptions and conventions, as well as those of the Adviser. While the use of an independent third-party industry pricing service can be a source for valuing the Fund’s CLO investments, the Adviser will not use the price provided by a third-party service if it believes that the price does not accurately reflect fair value and will instead utilize another methodology outlined above to make its own assessment of fair value. At the same time, the Adviser may create a pricing challenge to the industry pricing service, in which it asks the pricing service to review their price to bring it in line with what the Adviser believes is the appropriate fair value.

The following is a reconciliation of the fair value of investments for which the Fund has used Level 3 unobservable inputs in determining fair value as of June 30, 2026:

The net change in unrealized appreciation included in the Statement of Operations attributable to Level 3 investments still held at June 30, 2026, was as follows:

The following table summarizes the valuation techniques and significant unobservable inputs used for the Fund’s investments that are categorized in Level 3 of the fair value hierarchy as of June 30, 2026:

​(1)    The Fund generally uses non-binding indicative bid prices (“NBIB”) provided by an independent pricing service or broker on the valuation date as the primary basis for the fair value determinations for CLO Debt, CLO Equity, Feeder Fund Investments — Debt, and Feeder Fund Investments — Equity investments, which may be adjusted for pending equity distributions as of the valuation date. Each price is evaluated by the Adviser pursuant to procedures approved by the Board of Trustees of the Fund, including performance and covenant compliance information as provided by the respective CLO’s independent trustee.

​(2)    Weighted averages are calculated based on fair value of investments.

​(3)    The impact on fair value measurement of an increase in each unobservable input is in isolation.

​(4)    The value of New Mountain Guardian IV Rated Feeder III Ltd., Series 2024-2A (“NMRF”) is determined using a market approach, with the entity’s net asset value (“NAV”) serving as the starting point. A premium is applied to NAV to align the valuation with recent trading levels observed for securities with similar risk and return profiles. The premium is determined based on NMRF’s previous distribution as a percentage of NAV, to which a market-derived multiple is applied. The multiple is developed by analyzing recent trading prices of comparable securities and determining the premium at which those securities trade relative to their respective NAVs, expressed as a multiple of their recent distribution levels. This market-derived multiple is then applied to NMRF’s distribution rate to determine the appropriate premium to NAV. This approach incorporates both NMRF’s underlying NAV and observable market pricing for comparable securities in determining fair value.

Flat Rock Global, LLC serves as the investment adviser to the Fund pursuant to the terms of an investment advisory agreement (the “Advisory Agreement”). Under the terms of the Advisory Agreement, the Adviser provides the Fund such investment advice as it deems advisable and furnishes a continuous investment program for the Fund consistent with the Fund’s investment objective and strategies. As compensation for its management services, the Fund pays the Adviser a management fee of 1.375% (as a percentage of the average daily value of net assets), paid monthly in arrears, calculated based on the average daily value of net assets during such period. Prior to February 28, 2025, the management fee was calculated and payable monthly in arrears at the annual rate of 1.375% of the Fund’s average daily total assets during such period.

In addition to the management fee, the Adviser is entitled to an incentive fee. The incentive fee is calculated and payable quarterly in arrears in an amount equal to 15.0% of the Fund’s “pre-incentive fee net investment income” for the immediately preceding quarter, and is subject to a hurdle rate, expressed as a rate of return on the Fund’s “adjusted capital,” equal to 2.00% per quarter (or an annualized hurdle rate of 8.00%), subject to a “catch-up” feature, which allows the Adviser to recover foregone incentive fees that were previously limited by the hurdle rate. For this purpose, “pre-incentive fee net investment income” means interest income, dividend income and any other income (including any other fees such as commitment, origination, structuring, diligence and consulting fees or other fees that the Fund receives from portfolio companies) accrued during the calendar quarter, minus the Fund’s operating expenses for the quarter (including the base management fee, expenses reimbursed to the Adviser and any interest expense and dividends paid on any issued and outstanding preferred stock, but excluding the incentive fee). Pre-incentive fee net investment income includes, in the case of investments with a deferred interest feature (such as original issue discount, debt instruments with payment-in-kind interest and zero-coupon securities), accrued income that the Fund has not yet received in cash. Pre-incentive fee net investment income does not include any realized capital gains, realized capital losses or unrealized capital appreciation or depreciation. “Adjusted capital” means the cumulative gross proceeds received by the Fund from the sale of Shares (including pursuant to the Fund’s distribution reinvestment policy), reduced by amounts paid in connection with purchases of the Fund’s Shares pursuant to the Fund’s repurchase program. Effective July 1, 2026, the Board approved an amendment to the Advisory Agreement to change the basis of the “pre-incentive fee net investment income” calculation from “adjusted capital” to net asset value.

The calculation of the incentive fee on pre-incentive fee net investment income for each quarter is as follows:

•    No incentive fee is payable in any calendar quarter in which the Fund’s pre-incentive fee net investment income does not exceed the hurdle rate of 2.00% per quarter (or an annualized rate of 8.00%) of adjusted capital;

•    100% of the Fund’s pre-incentive fee net investment income, if any, that exceeds the hurdle rate but is less than or equal to 2.352% of adjusted capital. This portion of the Fund’s pre-incentive fee net investment income (which exceeds the hurdle rate but is less than or equal to 2.352%) is referred to as the “catch-up.” The “catch-up” provision is intended to provide the Adviser with an incentive fee of 15.0% on all of the Fund’s pre-incentive fee net investment income when its pre-incentive fee net investment income reaches 2.352% in any calendar quarter; and

•    15.0% of the amount of the Fund’s pre-incentive fee net investment income, if any, that exceeds 2.352% of adjusted capital in any calendar quarter is payable to the Adviser once the hurdle rate is reached and the catch-up is achieved (15.0% of all pre-incentive fee net investment income thereafter will be allocated to the Adviser).

For the six months ended June 30, 2026, the Adviser earned $2,702,497 in management fees.

Ultimus Fund Solutions, LLC (“Ultimus” or the “Administrator”) provides the Fund with administration, fund accounting and transfer agent services, including all regulatory reporting. Under the terms of a Master Services Agreement, by and between the Fund and Ultimus, Ultimus receives fees from the Fund for these services.

U.S. Bank National Association (“U.S. Bank”) serves as the Fund’s custodian.

The Fund has entered into a Distribution Agreement (the “Distribution Agreement”) with Ultimus Fund Distributors, LLC (the “Distributor”), a wholly-owned subsidiary of Ultimus, to provide distribution services to the Fund. The Distributor serves as principal underwriter/distributor of Shares of the Fund. Under the terms of the Distribution Agreement, the Distributor receives fees from the Fund for these services.

U.S. Bank and the Distributor are not considered affiliates, as defined under the 1940 Act, of the Fund.

The Fund conducts quarterly repurchase offers of 5% of the Fund’s outstanding Shares. Repurchase offers in excess of 5% are made solely at the discretion of the Board and investors should not rely on any expectation of repurchase offers in excess of 5%. In the event that a repurchase offer is oversubscribed, shareholders may only be able to have a portion of their Shares repurchased.

Quarterly repurchases occur in the months of March, June, September, and December. A repurchase offer notice will be sent to shareholders at least 21 calendar days before the repurchase request deadline. The repurchase price will be the Fund’s NAV determined on the repurchase pricing date, which is ordinarily expected to be the repurchase request deadline. Payment for all Shares repurchased pursuant to these offers will be made not later than seven calendar days after the repurchase pricing date.

The Board approved the establishment of a distribution reinvestment plan (the “DRIP”). The DRIP was effective as of July 2, 2018, and was first applied to the reinvestment of cash distributions paid on or after October 26, 2018.

Under the DRIP, cash distributions paid to participating stockholders are reinvested in Shares at a price equal to the NAV per share of the Shares as of such date.

In the normal course of business, the Fund enters into contracts that may contain a variety of representations that provide general indemnifications. The Fund’s maximum exposure under these arrangements is unknown as this would involve future claims that may be made against the Fund that have not yet occurred. However, the Fund expects the risk of loss to be remote.

The following table represents the Fund’s unfunded commitments on CLOs held by the Fund as of June 30, 2026:

The Fund has evaluated events and transactions through the date the financial statements were issued and has identified the following events for disclosure in the financial statements:

Subsequent to June 30, 2026, the Fund paid the following distributions:

In June 2026, the Board approved an amendment to the Fund’s investment advisory agreement to modify the calculation of the incentive fee so that the applicable quarterly hurdle rate and related incentive fee calculations are based on the Fund’s NAV rather than adjusted capital. This amendment was effective July 1, 2026.

A description of the Fund’s proxy voting policies and procedures is available without charge, upon request by calling 1-307-500-5200, or on the U.S. Securities and Exchange Commission (“SEC”) website at http://www.sec.gov. Information regarding how the Fund voted proxies relating to portfolio securities during the twelve-month period ended June 30th is available on the SEC’s website at http://www.sec.gov.

The Fund files a monthly portfolio investments report with the SEC on Form N-PORT within 60 days after the end of the Fund’s first and third quarters. Copies of the Fund’s Form N-PORT are available without charge, upon request, by contacting the Fund at 1-307-500-5200, or on the SEC’s website at http://www.sec.gov.

Profitability. The Board noted that the Adviser profited from its relationship with the Fund during 2025. The Board considered the fees and expenses of the Fund in relation to the Fund’s profitability and considered the knowledge and expertise of the Adviser. After deliberation, the Board concluded that the Adviser’s profits were not unreasonable in light of the services provided by the Adviser.

Economies of Scale. The Board discussed that the Fund was not yet experiencing economies of scale. The Board concluded that it would continue to discuss economies of scale as the Fund grew in size.

Conclusion. Having requested and received such information from the Adviser as the Board believed to be reasonably necessary to evaluate the terms of the Advisory Agreement, and as assisted by the advice of legal counsel, the Board determined that the continuation of the Advisory Agreement was in the best interest of the Fund and its shareholders.

Separately, at a meeting held on April 6, 2026, the Board, including a majority of the Independent Trustees, considered and approved an amendment to the Advisory Agreement to change the basis of the “pre-incentive fee net investment income” calculation from “adjusted capital” to net asset value. The Board considered that the impact of the amendment was expected to be economically neutral, and would align the Fund’s incentive fee calculation methodology more closely with industry peers.

Must be accompanied or preceded by a Prospectus.
Ultimus Fund Distributors, LLC is the Distributor for the Flat Rock Opportunity Fund.