It's my version of an armchair, as a person who likes being in small enclosed spaces and sitting on the floor. It's basically a 1m cube, with a frame made of scaffolding handrail poles, and adjustable faces made of plywood.
I started with twelve 1m lengths of 26.9mm scaffolding handrail, a bunch of three-way elbows and a bunch of single swivel pieces.
Assembling the frame was easy because the scaffolding parts all fit together with inbuilt grub screws.
The faces started as 1m squares of 18mm plywood. Nuts and set screws attached the panels to the swivels on the frame.
I didn't attach the top panel, so its weight keeps it there but it can still be removed. For two of the sides, I left the swivel pieces slightly loose on the frame which allows them to work as hinges. The result is that the cube can be arranged to have anything between three and six solid sides (or between zero and three open sides). It only took a bit of trial and error to make holes in the other side panels to stop the bolts getting in the way of the folding.
Tested for security by my rabbit.