Any good resource to understand how Layer 2s work?

I want to know how Ethereum layer 2 networks work on a technical level, especially Optimistic rollups such as Arbitrum and the OP stack. I want something detailed enough that I would be able to create my own layer 2 on top of a testnet if I wanted.

Most of the content I've seen so far are just higher level descriptions like it "aggregates transactions and posts them in a batch to mainnet", which really isn't satisfying to me.