Whenever I use clay, paper mache, and sometimes paint I always cover the table for easy claenup.
Warning: Clay dust will stick to the tables long after they have been washed and washed and washed!
1. Butcher paper is great, and you can fold it up and reuse it until it's way too gross.
2. Laminate sheets of paper to be used as placemats, or go to the dollar store and get placemats.
3. Rolls of painters plastic or plastic tarps.
4. Cut the seams from large garbage bags and lay them out.
Another tip: Instead of sponges, buy washcloths. You can wash them at home when they get real grungy.