I may have told you about this before, but it's just so darn handy that it bears repeating -- grids are good.
In the bottom of each damp box is a section or two of plastic grids which raise the foam supporting a piece up off of the damp plaster block, but don't block air circulation.
Out in the open air, lay them over wire shelving to form a nice drying rack that gives plenty of evenly spaced support to tiles or other flat-bottom ceramic ware.
So where do you find these great grids? In the lighting department of a hardware store -- they are actually those grids that sometimes cover fluorescent ceiling fixtures. They're inexpensive and easy to snip apart with wire cutters to a custom size.
No doubt there are other uses for these plastic grids -- I invite you to share your ideas in the comments section.