My fixture could be mounted on a wall with either 80/20 aluminum extrusion or plywood backing. Or for that matter a plate of aluminum or steel. The cones that hold the tubes can be adjusted to provide accurate frame alignment. The alternate V block assemblies made locally by one of my friends (with a CNC mill in his garage) are also height adjustable. While that method works well, it is not how I teach my students. I teach them to continually check alignment as the frame build progresses on a flat table.

I've checked local kitchen suppliers for granite or quartz countertops. I think they are around $35 a square foot. For that matter, I think my fixture on a maple butcher block bench top would work okay. Some flat steel plate could be put underneath in sections or the whole thing to catch flux drops or errant flame pointings. When not in use the fixture could be hung on the wall to make the bench space available for other tasks.