First I used regular paper to make masks for the areas I did not want to stamp with the background stamp. These papers are taped to the grid sheet and to each other but the card can be slid in or out. Which means that if I wanted to make a bunch of these I could leave the masks taped down and just slide cards in and out to do a stack. Then I stamped the background stamp over the whole thing.
When I pulled the card out it looked like this, just a bit of the background stamp on either end.
My next step was to use a ruler to mark off the "pieces" of the card. I used black marker to do that, then used a gray marker to add shadow.