Thanks playmofire, I might take you up on that later.
First I tried some woodwork. I do not have a jigsaw, so I made due with a normal saw (see pic) and some knives (see pics) for the first rough cut (pic 1)
I used my multi tool to clean it up (pic 2) and to cut the wall braces (pic 3). Now it is late. Tomorrow I will work on this some more.
Mind you, this is only a prototype. The parts are a bit on the rought side. I'm only exploring the techniques involved. Might buy some extra tools. Hmmmm, nice.
I used 4 mm plywood, 3 layers. My room smells like scourched wood now.