You don't want to do anything to stop the drying process. And you can't seal it wet. Pallets may work, but wherever the pallet touches the floor it will impede drying, perhaps not allowing it to dry at all. Metal racking would work, but it won't be cheap. Inverted plastic bread trays....about 4" tall could work. At any rate you will have to purchase something.....or you could tear out the floor now and replace the bad plywood.