About a month ago, DS2’s OT recommended we use a corner chair to help him sit up since he still can’t do it unassisted. They didn’t have any available for me to borrow at the time and they cost $100s to purchase so I made my own out of cardboard and duck tape. I’ve since glued on the anti-slip fabric used under futons and carpets. It’s all double layered cardboard from an old shipping box and pizza box on the bottom. It is stable and has held up well.