It's amazing how much pleasure this gives me, compared to buying something. It's made out of a scavenged old hair-cutting cape, some additional thicker fabric for durability, and 2 bamboo poles.

Here's some photos that are hopefully self-explanatory.

This is what it looks like, in use

Rolled up for storage

Laid out so you can see the structure. There's a folded over pocket that the bamboo poles go into. The poles are tied together loosely, to make it easier to assemble.

The poles are in the pocket, and crossed. Now you sit on the non-pole end, and lift up the poles behind you. It's not difficult.