Can I place a waterproof cloth under the baby to keep the dock clean or use the dock on a waterproof sheet?
We strongly advise against placing anything in the dock with the baby. Blankets (and pillows) present a suffocation risk if the baby should roll over onto baby's tummy in the dock, and can also lead to overheating. A child placed in a dock should be dressed appropriately for the temperature of the room.
Waterproof materials can also harbor heat, which can potentially lead to overheating, and can trap moisture, which can potentially lead to mildew.