Quick knit piece that can be done with very little yarn. I used acrylic for a more flexible fabric. I have also made it with cotton for a sturdier fabric which gives crisp lines when looking at the design. Make sure to leave a very long tail at cast on and bind off as piece is sewn on by wrapping the yarn around the straps.
Needle size and yarn weight is up to you, and how you want your shoes to look.