Here’s a cute box I taught last month – it all folds in on itself into a triangle. I can’t remember the measurements off the top of my head. For the closure, an extra piece of card stock was cut large enough to cover front and back of triangle and the back flap was adhered to the back, and the front was attached with a velcro dot which keeps the triangular shape.
We then used Collage Curios to decorate it with. 