I make my fidget mats about the size of a large placemat, reason being that it fits across their lap easily. (14 x 20).
This measurement is not written in stone but I have found that this is a good size. I put batting on the back of the front--this can be scraps --and lightly quilt that. when done, I pin the back piece right sides together, leaving appox 6 inches unsewn for turning. When turned, topstitch around edge. Sometimes, I do another topstitch 1/4 " from the first.
Then comes the fun. Small zippers with a ribbon pull, squares, triangles or circles of different fabrics(minky, silky stuff-usually double, fleece, suede). I have a bag of squeakers supposed to be for dog toys. That takes a 4 inch square which I stitch down--did I mention zig-zag- and stuff the squeaker in before the last edge is sewn. The county home that I donate the mats to seem to like them. By the way, the asked not to use buttons since some guests can tear them off and swallow them no matter how strongly they're sewn on. I found a roll of white organza at AC Moore and use squares of that, press under the edges, and before the last seam, pour in some sequins. Dollar store has them.
Lengths of different colored ribbons(no wire edges), folded in half, maybe the ends slipped under some the squares, sort of like a mini taggie. Pararie points work well also. Please note that these mats are washed in heavy duty machines and hot water and usually don't last more than six months. I have pics on my I-Pad but I don't know how to post them. Pics are worth a thousand words. Everyone, thank you for making these mats.
eri