NEWS - Who doesn’t like pistachios? Absolutely no one, that’s who. Let's face it the little green nuts themselves are great, but the shells, not so much.
I'd suggest putting the top piece on a fat dowel pedestal raised up a couple of inches. That way there would be more room for hulls to get pushed under the top section. Hulls take up significantly more room than the whole nuts.
Even with an indent or dowel I would always keep them separate when using them unless the bottom was significantly larger. I've hardly ever eaten them unless standing or in my lap.
I am thinking you could make a scroll saw version. Both top and bottom "trays" would be made out of a flat piece, say 1/2" with a outer raise ring, say 1/2" glued on. The bottom "tray" would also have a small block attached to set the top "tray" on. I would add a small piece of dowel to the top of the block so the top "tray" would sit securely but be removal. The beauty of a scroll saw versions is the "trays" could be just about any shape you wanted. I can visualize it. I just wish I could do graphic design on a computer to show you what I am thinking.
Scott, good idea. They are all card players so ones made in the shape of hearts, spades, clubs, and diamonds would be cool. Maybe just shape the top tray and leave the bottom more plain.