: Some people have used aluminium ladders as a base on trestles. Attach plywood
: plank with brackets from below to rungs and put the risers and forms on
: that.
: JohnK

Yep, a ladder will work. I screwed the plywood directly to the rungs with drywall screws w/o pilot holes; the screws self-thread into the rungs and when removed leave only small holes. Simple, cheap, and stable. Also lightweight, which was important to me, as, lacking workspace, I had to wheel the whole operation out onto the driveway to build.

(For Shooting Star builders, the photo shows my screw-up in sanding through the stern, plus the extra 1/2" or so of "skegginess" I built into the stern keel in response to some notes from Ken Katz, re: tracking.)