I make a lot of segmented bowls. Glue the segments together, belt sand, then glue the rings together. (If you have room for the clamps). Several years ago I made this simple, temporary set-up. The round ply plate has a 2-1/4" hole. (Fits my lathe chuck for other uses.) I have about 20 different diameters of these for different size bowls. The small piece is 2-1/4" with a dowel hole for alignment. I call it a bushing for some reason. The bottom is a 2x4 hole sawed 3-1/4" with a "thru" dowel that fits in the hole on my assembly board. The reason for the bushing is that some of my plates are too big to hole saw in my little DP. Thought many times about some modifications but "if it ain't broke, don't fix it".