Have you seen the post of people using pennies for floors?
That is where this idea came from.
I spray painted the tray.
After it dried I used Mod Podge and put it on a section of the box.
You will have to work quickly.
I put out a few rows and them just kept adding more Mod Podge to the bottom and
starting to add it to the top and fill in the gaps between the pennies.