I did something similar to this as well for growing water cress but it was not so fancy! I used the styro foam trays blood collection tubes come packed in (they kind of look like this: Blood Collection Tubes Packing Tray-Blood Collection Tubes Packing Tray Manufacturers, Suppliers and Exporters on Alibaba.com
) - these trays have little "cups" in rows all over the surface for the tubes to stay upright. I poked holes through the ends of the cups and stuck the water cress stems through. The water cress did great this way and I used them in my daphnia tub. I bet any medical office would give these used trays away - the vet clinic where I work goes through several every few weeks.
I was pleased with the outcome of my simple trays, but nothing as fancy or near as nice to look at as yours, Eva! Bravo!