Edit: I found this link which is helpful. Still not sure how to actually implement it.

Examples of using each cost basis accounting method
Let's assume that an investor purchases 5 BTC over time, with the following prices and dates of purchase:

- January 1, 2021: 1 BTC for $10,000

- February 1, 2021: 1 BTC for $12,000

- March 1, 2021: 1 BTC for $9,000

- April 1, 2021: 1 BTC for $15,000

- May 1, 2021: 1 BTC for $18,000

The investor sells 3 BTC on September 1, 2021, each for $20,000 for a total of $60,000

Using FIFO:

Under FIFO, the investor will sell the first three BTC purchased: those bought on January 1, February 1, and March 1. The cost basis will be calculated by adding the purchase prices of those three units as follows:

- Cost basis = ($10,000 + $12,000 + $9,000) = $31,000.

The profit realized on the sale will be:

- Profit = $60,000 - $31,000 = $29,000

Using LIFO:

Under LIFO, the investor will sell the three most recently purchased units: those bought on March 1, April 1, and May 1. The cost basis will be calculated by adding the purchase prices of those three units as follows:

- Cost basis = ($9,000 + $15,000 + $18,000) = $42,000.

The profit realized on the sale will be:

- Profit = $60,000 - $42,000 = $18,000

Using HIFO:

Under HIFO, the investor will use the three highest-cost Bitcoins as follows:

- Cost basis = ($18,000 + $15,000 + $12,000) = $45,000

The profit realized on the sale will be:

- Profit = $60,000 - $45,000 = $15,000

As you can see, each cost basis accounting method results in a different profit and tax liability for the investor. It's important to understand the pros and cons of each method and choose the one that works best for your specific situation.

https://www.accointing.com/en-US/blog/crypto-cost-basis