A couple of pictures showing how I use the Tyvek when forming card slots in Wallets and Clutch purses
Of course you can use the Maker's Leather Supply templates or make your own, the origin does not matter
First I make several pockets at a time and have them ready to go.
Since the template is the right size I use it for reference and cut a old card down to the proper size for forming the pockets.
From there it is a matter of fold, crease and repeat.
When time comes I get everything set up for pocket installs. Not rocket science just glue and sticky fingers.
Spray the adhesive lightly onto the leather but be sure and have an even coat. Ignore the uneven edges they are unseen and I was to lazy to trim them.
Almost done, I spray the Tyvek with the spray adhesive so when the back is folded into place nothing moves.
Once the pocket has been rolled smooth so you know the glue has made good contact it is a good time to take a slender tool and make sure the spray adhesive has not bonded the card slots shut.
I get in the habit of putting old plastic cards in the slots at least over night just to be safe. Also a reminder not to sew the slot to small, don't ask.
Now a good thing to consider is having pockets like this and other sizes for experimenting with new shapes and styles of wallet. It is much easier to visualize with actual parts instead of just sketches.