Ask HN: BTree Alternative for Storing to Disk?

I am learning how to write a database for fun.

The issue with storing BTree to disk are the many operations for balancing on insert and deletion. I want a structure that is very simple to write to disk that doesn't require "balancing".

I tried making a HashTree for unique indexing which basically creates a new hashmap on each collisions, which would simplify appending the new hashmap into a file on disk. The issue was the hash function was difficult to craft that avoided going too far in depth through consecutive collisions.

I'm thinking there must be an alternative structure, but my limited understanding and research has yet to reveal anything better than BTree, LSM tree or Skiplists.