u/Adept-Association848

I am sewing a tie waist dress and just using one that fits me well as a blueprint. I’m stumped on what these (stays?) are made of / called / how I can make them. Anyone familiar with them?

In case it’s hard to tell from the pictures — they’re sewed into the waist of the garment for keeping the belt in place (and let me cinch in the waist nicely too!).