It was very easy, actually; you start with a pair of flip-flops and some craft foam. You use the craft foam to give the sandals the strap over the foot and the straps that go around the leg all the way up to the knee. Mine are crossed at the back because...well, I think they actually are in the character since we don't get any shots of him from behind. The sandal straps close in the back with velcro, use hot glue and metal pins at the bottom of the foot tomake sure the straps stay attached to the sandal and red acrylic paint. Good luck!
Thank you. The answer to your question might be a little vague seeing as how most of the costume was just sewing. The sandals were made from flip-flops and craft foam and almost any other accessory you see is also made from craft foam.