Summary

A quickly drawn flip flop designed with 3D printing in mind.

How to print:
1) First slice and print the cushion tester using recommended settings because every TPU or flexible filament is different:
1 or 2 walls, with an extra wall every other layer (wall thickness varies with nozzle width, I use a .6mm nozzle and 1 wall with +1 wall every other layer)
Gyroid infill, start with 7%. (softer filaments will need more, stiffer filaments will need less)
approximately .64mm of bottom layers. (The parts of the flip flop print upside down, so the bottom layers are actually the top and vice versa. I use .32mm layer height. With a .4mm nozzle I'd use 3 .2mm layers)
approximately 2-3mm of top layers.
No supports or brim
Other settings will depend on your printer and filament combo.
2) once you are satisfied with the cushion and shock absorption of the tester, print the Flip Flop Base. At its default size (maybe size 12 US men's) it will fit on a 235mmx235mm build plate like the Ender 3, but just barely, you have to make sure your slicer settings have your build plate set to 235x235. (In Cura the default is 230x230) If you have smaller than size 12 US men's feet you can just measure your foot then adjust the size accordingly in your slicer.
3) Print the band with 100% infill.

It may be Easy to print, but there is some difficulty in assembly. Getting the band into the slots that are in the base of the flip flop will require some muscle. I use a large screwdriver to push them through. they are even harder to take out which I have not even been able to do.
There is SOME permanent tightness adjustability in the band. Instead of using super glue, fill in the gaps between the band and the base with hot glue for a tighter fit.