On picture you can see first version.
Leather, hard one, and thin one.
Friend with Sewing Machine.
Step 1: Draw, cut, glue
Use scissors for sponge, scalpel for cardboard holes.
Step 3: Glue, cut
After cutting, glue around.
Stretch a leather around the cardboard.
Step 4: Sew (option)
Also you can sew around cushions, but, not necessary. I did it, but I recommend it not.
All you have to do is cut holes on leather, and glue it for rubber sole.
But watch out, first add leather stripes and glue them from the inside to cardboard..
First version of sandals had no cushions, and no threads.
You can do it with no cushions, same instructions.
Step 5: Leather stripes, conclusion
Joint of adoptable stripe is made with Velcro tape.
(note: version 1.0. on this pictures)
Version 1.0 Vs. 1.1.
Version 1.0 is more comfortable than V.1.1. also durable and easier to make.
Version 1.1. looks better.