I don't remember where I saw it but yes the starting point is just a circle.
Roll the edges (almost but not quite edge to edge) together adhere and then when you fold back you might want to dampen the center a bit to give it some pliability for the fold over. The corner when folded up or back...I saw them tie with ribbon to keep it closed. I myself wold probably fish the ribbon through the opening and then tie it up.
I can't remember where I saw it but they person also tried it with a square and it looked pretty cool.
Hope I made sense