Custom Generation "Type"

What I need to know if there's a way to make your own generation type.

What do I mean by this:

You've most probably seen how there are different options when it comes to making your world. There's Normal generation, Superflat generation, AMPLIFIED generation, etc.

I want to know if there's a way to make one of your own to add your own content in.

If there's a "procedure" way (which I doubt), just tell me the blocks I need to make it.

If the solution requires coding, I'd be most grateful if you could show me what I should do in order to make a generation type of my own and the way to add my content to it (biomes, blocks, structures, etc).