I started clay works with my K-2 kids this week, and I am happy to see that the clay boards I made 3 years ago are holding up just fine. I can't recommend these highly enough if you use clay in your artroom!
Before I made these, I had some dusty, shaggy burlap mats that left clay dust all over the table, and slid around a lot when kids tried to roll slabs and such. It was a clean up nightmare, trying to keep the tables in decent shape changing from class to class and project to project. So...
I measured my tables and realized that a single board per table would be too big and heavy, so I made two per table from thin plywood and wrapped them in canvas. Here is the back view (still really clean after 3 years!):
They are heavy enough to stay in place but not too heavy. The key is to keep the dirty sides together and the clean sides together. For example, on each table, fold one over the other like closing a book, stack them on your rolling cart, and the clean side faces up. Then roll to the next table and do the same. This keeps the dust inside. I have a little mini broom and dustpan that we sweep them with if there are a lot of crumbs. It takes a couple of minutes to pick them up and the tables are perfect for the next non-clay-using class! Here's a pic that shows the cart I store them on in the back:
If I remember correctly, it was about a $60 investment but so so worth it. You can roll coils and throw slabs until your heart is content! I remember the first few times we used them, water and slip pills caused them to bend very slightly, but keeping them stacked on top of each other solved that problem overnight. Something to try if you haven't - happy building!