How I create something like this?

Hello there! I currently saw this post by San33 on Patreon where they made a pose that replaces how female sims stand while in CAS. NOT a trait pose though. Its very similar to the Stand Still In Cas mod, except San33 uses a custom pose. I really wanted to make something like that but for my male sims. I searched up and down the internet for mods and tutorials, but nothing was found. I'd love to learn how to make my own! Please let me know if you can help!
here's the post: www.patreon.com/posts/333-01-52518451