I asked if the student also put things in his mouth but the SLP said he primarily liked to squish with his fingers.Well, I didn't have a lot of squishy things at home or at work so, of course, I headed over to my favorite spot--Goodwill! Fortunately, they had swim "noodles" that day so I bought a couple. Our therapy assistant gave me a ratty, double tri-wall board that had been covered with wood-grain Contact paper, some sticky back Velcro, and I was all set.
Today my DH (dear husband) used our 80's electric knife to cut lengths of the noodles and then slice them open like a hot dog bun. (Yes, yes I do know how to use the electric knife but we had to have some "family time" this weekend.) We also cut some noodle "coins" for extra squishing opportunities. The foam sliced very clean with few snaggy edges. Many students with autism get very distracted by snaggy edges, I've found. I put duct tape on the short ends, then clamped the foam on the long ends.
Unfortunately, I had placed some removeable squishy objects on the board prior to attaching the lengths of foam, and learned that I had put the removeable objects too close to the edges. Oh well.
We'll see how this works for the student.