Welt pocket
From Squirrel's Lair
https://threadtheory.ca/blogs/tutorials/welt-pocket-tutorial
Follow those instructions Plus:
- make slot 1.5-2 cm wider than item it's for
- make the welt and base interfacing 5cm wider than that
- make the pocket strip 5cm wider than that
- make the welt piece about 12cm high
- put the center of the welt slot about 1/3 down on the welt piece
