Once that was completed (and luckily for me, everyone finished at different times), I got them to stand on their shoes, while I poked holes in the cardboard with a wooden skewer where the straps needed to go (two holes close together in between the big toe and the second toe, and another two holes, one on each side of the foot. Then we threaded a pipecleaner up through the two holes between the toes and twisted it a few times to secure it. The kids added some beads onto the pipecleaners and then I threaded the ends into the holes at the sides of the foot and taped them down on the underside to finish the flip flops
Here are eight of the nine pairs (one was still being worked on)This was a really good project for a lot of preschoolers at once (aged 3 to 5). They were all very proud to have made their own custom shoes to take home.