The trickiest aspect of the drive module was fixing it to the bottom of the turntable without interfering with any of the frame members. Recall that the lazy susan base is actually too large to fit the originally-planned site, and I had to route away some of the benchwork frame members to accommodate it. They’re still there, but they cover part of the outer ring of the turntable.
In the photo, the pink lines represent the location of the benchwork frame members. To mount the gearbox over the middle of the turntable, I cut a piece of scrap plywood that supports a stout arm over the middle of the turntable. The arm is glued and screwed to the plywood, which bolts in turn into captured nuts on the back of the outer ring of the lazy susan base.
This means the whole thing can be disassembled from beneath for servicing. The drive slides into the turntable, and after the four bolts through the lazy susan ring have been unscrewed, the module can be removed for access to the screws that hold the lazy susan base to the underside of the benchwork.
I have almost four inches of vertical clearance in this location, and so, I didn’t try to optimize for height at all. However, if I were building a multi-deck layout, I think I could fit this mechanism into a space less than 2.5 cm (1 inch) deep.