Interesting. Do those little cells have false bottoms in them. That tomato seedling looks like it's root is several inches long and would have to have extended out the bottom of the float tray.
This method looks pretty involved and probably wouldn't be as compatible with the northern growing zones. I would be interested to see it in person though.
Bruce

The styrofoam tobacco trays have a hole in the bottom. Looks to me like they'd take a 4X8 sheet of CDX, put a 1X2 around the edges, lay the plastic in, put in some 1/2" spacers, fill with 1" of water, and lay the wet trays with seeds into it. Don't know how far north that tobacco was grown. Guess Kentucky was about the limit. It does get cold there too...