The idea is that the forms will screw together, get lined and poured, and after the stone mix hardens enough, get unscrewed to remove the raw concrete sills.
At this point, the forms can get screwed together and re-lined and re-poured with the next batch. The raw sills can then be painted/colored, textured, and whatnot, then they go underwater for a week or so to do what's called "wet curing", which increases the strength of the final piece.
Since I'm only making six molds, I'm gonna need to do something like five sets of pours, possibly six. Maybe more if I break any of the sills before they're cured.
Once they're cured, they come out for final inspection, final coloring and detail work as needed, then they get sealed with a heavy-duty stone sealer. After that, they're ready to go up.