Damping between shelves and sandbox


My turntable is sitting on a sandbox. On the top of the sand I have an inch and two inches thick maple board. Between these two wooden boards I am using cork coasters. I`d like to find a better solution, but I don`t really want to use glue. I am thinking to get a non slip mat, but searching for better alternatives.
What would you use?

Both, the turntable, and the int. amp sitting on a DIY sandbox and plinth. The plinth is a bit smaller than the box, so It`s not touching the wood corners but sitting on sand. But, handling sand can be messy sometimes.
What would you mix with the sand so It`s not creating dust?
128x128korakotta
Try it with just the one thicker maple board.  Two boards and the additional interface probably create their own resonance problems.  This is something that can only be determined by trail and error.  Years ago I used a sandbox and found it was very effective, but I abandoned it because it was too messy.
ah yes, the old sandbox days
IMHO, these are easily bettered by replacing with Machina Dynamica Springs. They have various sizes to meet your needs. Contact Geoff for his expert advice. Oh and very inexpensive

hth
Check out the constrained layer damping product offered by ASC (the Tube Trap company), named Wall Damp. It's just what you're looking for.