found 10 cafeteria trays in a junkpile. they are 14"x18". perfect size,perfect price
They are almost perfect. Because they are so shallow your hive will need to be quite level, and they will be easy to spill. I would use them if I found them though. I'm using disposable aluminum turkey pans for mine - just the right size for 8 frame hives and about 3 inches deep. 1 1/2 - 2 inches deep would be perfect IMHO.