How do they make these one piece scales. Is some sort of milling machine needed?
If I was doing that I'd start with a decent sized hunk of wood and make the slot first with a jig and a table saw. Then I'd smooth out the inside of the slot, put a spacer in there to hold everything steady, and shape the outsides of the scales.
Of course, I've never made my own scales so I'm in theoretical territory here. I might try that and wind up having to turn my first few attempts into normal scales.
Maestro Livi uses a band saw. I think Tim Zowada does too, based on the appearance of the inside of the scales.