How to make custom wood and leaves, plus the other required items related to it?

Making custom blocks for logs and leaves is easy enough.

Easiest way to make a tree is to make a custom biome with it. An option for custom trees is there.

BUT if you want it to have a custom shape or want to spawn it somewhere else, maybe start with a tutorial from this guy:

https://www.youtube.com/c/NorthWestTreesGaming