This idea popped up in my head, and I decided to make one. I had no patterns, so I took two pieces of paper and folded them in the size I wanted. It did not work out 100% as I wanted, but I can still use it, and I'm pretty satisfied with the result.
It's a little difficult for me to explain in English how I do by folding, so I have made this tutorial. I hope it can explain how I make it.. What I meant by the edges, I mean "the sharp parts" i have marked with red - What do you call them in English?