How to make a homemade soap?

I was always interested ho at how to do things at home, and the soap just seemed to catch up my interest. I watched a few videos but I still have a lot of to learn.

The first video is the easiest tutorial and it requires only a few ingredients.
The second one is a bit complex, but I saw a lot of people selling that soap, still I need to learn why it is so popular.

This is what author uses, not me, I am just placing it here to have it as a list:

Lye Calculator??

^{Web | Discord | Steemit}