This is a recent project of mine using plywood from a previous project.
Some of the details:
-1/2" hardwood plywood finished with glossy polycryclic
-1/2"x1/2"x1/8" angle iron runners on the inside
-1"x1"x1/8" angle iron on the top to put hot pans on as they come out of the oven
-xenon lights on the inside middle
-for humidity I put a damp towel on the griddle with the griddle set on 'low'
-this proofer holds 6 full size sheetpans with room for the bread to rise
There you go, let me know if you have any questions.