[Aegis]

You could use a block of wood for the platform, just make sure that its been sanded down so the hamster doesn't get splinters, and there aren't any chemicals on it. A small cardboard box would also work, but the hamster would chew through it faster. The wooden block or cardboard box should definately be elevated above the bedding, so maybe use a small block or a mini-ladder so that your hamster can climb up into it. A way to make it safer is to glue the sand bath onto the platform so it doesn't slide off, or use velcro so that when you remove the bath off the platform it will be easier to clean.
-Aegis