(The word "kozaiku" has somewhat negative connotations, as in, "you should really get down to the root of the problem instead of just patching things up" but I'm all about little hacks for trivial things like clothing.)
I crocheted belt loops on my batik shirtdress. I was given this dress as a gift. It’s the right size, but the cut is a bit boxy for someone my build.
I thought about adding darts or slimming the sides, but the design of the dress made this difficult, so I decided to crochet belt loops to the side seams and tie it in the back with black ribbon.
The dress also had a seam that was coming apart, so I stitched that up as well.
Apparently I have an H body shape.
Cinching the waist with a regular belt or tying a self tie in front doesn’t work for H bodies, but the tie in the back styling does. I can’t remember where it said that H types were supposed to tie belts in back. It’s not something I discovered on my own. I think it was a YouTube video. At any rate, it's simple (especially if the dress already has a self tie belt) and it works, if your body shape is like mine.
I chose grosgrain ribbon because grosgrain is resistant to fraying. Unfortunately, it doesn't slide as well through the belt loops the way satin might. If you use a satin ribbon, you'll need to do something about the edges like paint them with nail polish top coat and cut through it when it's dry.