Diy ideas welcome/ posture correction

I don't use Pinterest so this may not be the right group, but it says diy so here go

Hi I like to make diy things with whatever random materials I have around.

I want to try to make my own reusable pads (maybe with old bra hooks since I don't have another type of clasp?)

Anyway I also want to make something that will help me correct my posture. Idk how to go about this one though. I know I can basically just use a strap on my shoulders but I want most of the support for my lower back.

I was thinking of finding something very firm that I can put against my spine and somehow tie in place, so that any slouching would immediate be uncomfortable and/or almost impossible.

Ideas welcome, I can't afford to just buy a brace or anything, but my posture sUcks and I want to look/feel more confident