re: Outer Ring Blanks

Not having a CNC, I figured what would I do to get that trough. If it was the correct diameter, a cove cut with the matching tablesaw blade would work, but what if it was not a common diameter?. Skew the cove cut, but then it wouldn't be circular (ellipsoid instead). Your last photo was the money shot.
Get it close, then use the main part as a sanding block. 
Brilliant!