A replacement sponge isn’t expensive, but often they come in a quantity that I won’t use in my lifetime. So I sought an alternative and used something that I already had around the house.
Step 1: Collect stock and prepare tools
To trim and prepare the sponges, I used a wooden straight edge from a home improvement store that I had lying around, and a utility razor knife. A metal straight edge would be better but I didn’t have one that would work well for this. Something to draw markings would be handy but not required.