I had made this ring stack a while ago to promote reaching and using 2 hands. My clients really enjoy looking at the photos attached to the plastic. I had laminated the photos and some clients sewed them to the plastic that I had cut from large detergent bottles. But you can glue pictures to plastic or cardboard to use for stacking. There are may ways to make this. I inserted the 2 tall dowels into a large bottle and then inserted that inside the box and covered it with contact paper to look nicer.
I attached a beeping toy by wrapping it up in fabric and then tying the fabric to the dowels. When they press down with force, they can hear the sounds.
This was a lot of fun . You can grade the difficulty level by making the holes in the plastic pieces larger or smaller.