Gertbysea, I also sometimes use those trays, but always line them with glad wrap as I think the foil is not good to be in contact with food.
Here's a "trick" I use when preparing several flavors of ice cream from one basic (vanilla) batch, so as to have flat slabs for use in cakes.I ladle the ice cream into ziplock bags and lay them flat on a sheet pan with the end that opens turned up and pushed up against the side of the sheet pan.Each pan will hold 6 of the 1-liter size bags and the ice cream freezes rapidly because it is thin. They can then be inserted into a stack of thin slices of cake (or cakes) Wrapped tightly in plastic wrap and put back into the freezer with a weight on top to compress them.When sliced, this is very pretty with the alternating colors and textures.