Quarry spalls are much more irregular than bricks, so it’d be a much rougher edge. Sounds like the edgers are the desired product, so by all means that’s what mattera.

For the concrete edgers I’d just lay an inch or two of sand and tamp it down firm. A tamped sand foundation is much easier to set and keep level than your average soils, and better for drainage and seasonal shifts (freezing). You’ll be having to keep 80 concrete edgers straight and even instead of maybe 10 wood boards.