I just put 750 yoyo's to a muslin backing. I did a whip type stitch around all of them to the backing. I did not prewash the backing and when I washed the finished project the muslin shrank just enough that all the stitching was not seen. Years ago my mother attached them to a backing by flatening them and did a hand quilt stitch around the edge of each one of the yoyo's about 1/8th inch from the edge.