Fast and Easy Half Square Triangles

I came across this site by Amy Gibson, Stitchery Dickory Dock, with a tutorial for making fast and easy half square triangles:

http://www.stitcherydickorydock.com/hst-trick-its-not-cheating-its-genius/

I estimate that when using pre-cut 5 inch charms, the resulting half square triangles will be 3-1/2 inches by 3-1/2 inches. When using pre-cut 10 inch cake layers, the half-square triangles will be approximately 7 inches square.