The hundred board is a truly amazingly open ended toy. Here is a brilliant way to use it (Credit @seiswf ) Constellation builder ⭐ We will adding this to the list of activities for us! .
Other activities we have tried are pattern making (it can get pretty challenging with colorful balls), mapping (start from "home" and mark a spot as destination, go 2 tiles north, 2 tiles east...), do a mirror image (set up a pattern and make the littles reverse the pattern to have a mirror image, for my kids this is a challenge wr are still working on) and the usual counting to 100, skip counting, simple arithmetic calculations, etc. You can find the board in the shop.