How do I create a custom texture atlas?

[Pomegranate]

I'm new to modding, and I'm currently working on a 1.20.1 mod. I want to create a custom texture atlas, but I'm having trouble figuring out how to set one up. I’ve looked around for documentation and tutorials but couldn’t find much.

[Scrobatto Studios]

idk if im right, but i think that minecraft dont use texture atlas anymore, maybe imi wrong tho