I checked out a copy of this marvelous old book from 1959 called Creative Paper Craft by Ernst Rottger. Had to get it on inter-library loan, as it’s now kind of hard to come by. (and then all the libraries shut down, so I’ve gotten to keep it for a nice long time!) Among other things, it has some fun exercises for cutting and expanding one sheet of paper, either by moving the cut pieces farther away from each other, or flipping them out from the edges. Below is one of my experiments in cutting and flipping.