Dear Hubby made them from quarter inch acrylic. They're resting on wood blocks on either side. Before that I had suction cup mounted shampoo bottle holders. When you water you periodically need to re-press the suction cups. Here's a photo of that: Orchid shelf from suction cup shampoo holder by Gardentheater, on Flickr
Not as nice looking but easy.
Thank you!!! My husband is not handy . Suction cups shampoo holders for me. Do you by any chance remember where you got yours?