The base flip flop is made of 100% rubber. These are not the cheap foam flip flops you get at a craft store. My flip flops here are made in Brazil by a company called Cariris, distributed in the USA. They are very durable and will not get all squished up after a few uses.
To make them pretty, I use macrame knotting technique to cover the straps, adding a crochet flower on the top.
See how to make this on my Youtube playlist.