I found some extremely fine stainless steel screen on Amazon and bought three 12 inch square pieces. Went to the hardware store and bought three pieces of 1/8" X 3/4" flat bar 40 inches long.
I bent the flat bar into 10 inch square frames and clipped the screen inside the frames with bulldog clips. I now have three 10 inch square spice smoking trays. The screen can be easily removed for washing and easily replaced.