How to Make a WordPress theme? to code or not to code? PLEASE answer

Sup peeps.
I have a question, I’m very good designing and coding regular websites but I suck with wordpress. I know php, css, and all that stuff but WordPress confuses me.

I’ve been reading a couple of tutorials and the best one that I found was

https://www.webdesignerwall.com/tutorials/building-custom-wordpress-theme

It tells me to code the design that I already made as if it was a regular old design not meant for WP and then I simply add small php code to the already created code which I will then use for my WP hierarchy pages.

Is that how you regular WP coders do it, or do you simply code and slice your design into your soon to be new theme?