You might consider doing what a bunch of others on here have done: CAD (Cardboard Assisted Design) Get some thin cardboard, the thickness of the stuff they use make the free USPS Priority Mail boxes is pretty good but other thin, non-corrugated cardboard will work. You may have to experiment, but when you finally get it all cut and folded and fit up like you want it, just lay it out flat and there's your pattern. Trace the shape out onto thin sheet metal or aluminum, cut it out, bend it up, and you've got your tray.