Step 1: Cutting and folding
I started with a piece of Tyvek 4 times the height of the check and a little wider. IT was about 10x14 inches. I folded the sheet in half then each of those in half as well. One fold will later house the cards, one the cash and receipts, and the "hidden compartment " on bottom would hold the checks.
Step 2: Securing the sides and adding cards.
I made the cuts for the cards with about a quarter inch of space between cards. I made a second slot above the first along the same lines.