Dampen the sponge or towel.
We tested the sponge garden activity with a variety of sponge types - natural, artificial, paper and fabric towels. We found any type worked.
Put your sponge or towel on a plate before getting it damp because you will need to move it, and you want to protect the surface underneath it.
We tried the garden where we pushed the seeds into the holes of the sponge, but we found it didn't make a difference whether the seeds were just on the sponge surface or in a hole.