So today I translated that idea into regular size greeting cards. Here is my first try:
I wanted the DSP layer to measure 5 by 3 3/4, but to be able to space the 2 pieces apart like that once cut on the diagonal, I started out with a piece that was 4 by 3 3/4!
The white layer behind is 5 1/8 by 3 7/8
Very easy actually!