Go for cheap nursery polypots, less than $1 each at the grow store.
Take a couple 2x4's. Cut them so you have a couple pairs with a length that is just shorter than each dimension of your floor.
Lay them on the floor.
Spread a pond liner or a couple layers of the thickest plastic sheeting you can find.
Voila, problem solved! Instant spill containment courtesy of the local grow shop guy, who knows I can't afford to be buying a bunch of rigid plastic just for a floor protector, lol!