Thanks for posting that video. My medium-term goal is to make a tote bag like that, but instead of turning the side edges out and stitching suede sides together, I would want to skive them down, overlap them, and do a double row of stitches.
The two halves of this box kit seem to follow a similar process to the bags linked here, except that instead of cutting the material away from the large rectangle of leather, that material pivots inward and is riveted to the base. It seems simpler and also reinforces the bottom of the bag. Useful for square shapes like this box kit but it would create an uneven base in a rectangle like these bags.