(First of all, sorry I have no pics for the steps.)
First you need to get a pair of old flip flops or a pair from the dollar store if you like them enough!

Cut out a bunch of 3'' pieces of fabric about 1cm wide. As many as needed to go around the thong part of the flip flop. Different sizes may vary.

Take all of your pieces and stretch them out.

Tie all of the pieces next to each other (double knot it) all the way across the thong part until you've covered the shoe with the cloth knots.
(This is an example of loom strings).

Then do the other shoe and slip them on! Wear your new awesome shoes!:)
(Another example with different string).