Dress up plain flip flops with paracord. Use the same method that you'd use for a bracelet, but use the strap of the flip flop for the center. The tutorial in the attached link shows how to make them by completely removing the strap.
Refashion your old flip fiops into DIY comfy braided strap sandals using old t-shirts or jersey fabric and a pair of scissors. Full Tutorial on Website.This is good because flipflops always fall off my feet