Hi Folks...
... I have been using the plastic flats that are used in the bedding plant field. They are 10 by 20 by 2 1/2 inches deep. some have slots in the bottom others have a solid bottom. I put a tray with slots in a tray with out slots. My slotted tray holds 2/3 compost and 1/3 seed starting material. I add about 6 Tablespoons of dried sea weed, 6 Tablespoons of green sand and 4 Tablespoons of ground up egg shells for nutrients. I mix the above amendments with the bottom half of the growing medium before I add the top half. when I water I lift up the top tray and put about 14 ounces of water in the bottom tray. The roots go through the slots in the upper tray pick up the water in the bottom tray. This keeps the top of the growing medium as dry as possible minimizing the mold problem. I had a friend try the trays you talk about and she had all kinds of problems trying to figure out when and how much water the wheatgrass needed.