I've been looking for humidity trays that will fit in my growing areas and have not had much luck. Good thing I'm Plucky! I also have the good fortune of having boxes of hardwood scrap lying around. So....
The materials:
1/2" X 1 1/2" teak for sides
1/4" plywood for bottom
Black door and window caulk
Brass nails
Wood glue
5 pounds of small gravel
All together this cost me about $17 mainly 'cause I already had the teak stock.
The Process:
First, I cut all pieces to size. Then I cut a 1/4" rabbet on bottom of all teak pieces.
Once the pieces are ready, assembled with wood glue and nails. Like my clamp system?

After the glue dried I sanded and masked the outside edges.
The caulk was actually my second try at waterproofing the inside. I first tried a spray-in bed liner (you know, for trucks) but it just didn't stick to the teak very well. The caulk sticks well but was hard to coat evenly. The trick to coating the inside was working fast! I used my caulk gun to lay out 1/4" beads of caulk at a rate of one per 1/2" of exposed wood. I smoothed and smeared the caulking around with a metal putty scraper that I'd dip in mineral spirits. The mineral spirits help to keep the caulk from sticking to the scraper and helps to make a smoother finish. Once the sides and bottom were well coated I ran another bead of caulk around the corners then smoothed the corners with my finger (dipped in mineral spirits again). After it was done.
After the caulk dried I finished the outside surfaces with food-grade mineral oil, wet sanded with fine steel wool. The final step was putting in the gravel, setting it in place and filling with water. The final product.
Not only to I think it displays my phals and neo better, but the fiance really likes the look! It is also doubling as the reservoir for the carnivorous plant in that room. Gotta love some good multi-tasking!