Based on https://www.thingiverse.com/thing:4648523/ for the main form, just added a few bits and pieces.

I found the back pattern didn't print well with my printer and TPU, so I blocked that off and added a cutout for the logo.

I also added soft buttons to cover the phones buttons and seal the case. This worked better with the TPU I was printing with.

Printed at 101.5% scalling fitted nicely on the iPhone 12. Earlier prints at 100% didn't quite work.