Hi Stuart,
I used a wedgie sled and set my table saw blade at a 23deg angle (You can pick any angle you like but a 20-25deg angle looks ok) I used 18mm ply and milled strips 18mm - 22mm wide depending on the shape of your bowl. Now here is the trick when you saw the segments you need to mark with a pencil the segments that come off the front arm of the sled(f1,f2,f3 etc) and the segments coming off the back arm of the sled (b1,b2...etc) Why is that so..you ask. The reason is you choose only one set of segments either all the front ones or all the back ones to make your ring. You then cut a few strips of ply length wise same angle both sides for your spacers.
Then the fun starts trying to glue up the ring because with the angles involved you cannot put a rubber band or any ties around the ring because they will just pop out. I glued two segments with a spacer with a rub joint until the glue held firm then repeated the exercise until the ring was complete. Once all rings are complete I lightly sanded them all in a drum sander just to remove excess glue and get the spacers down to the same height as the ring.
After that its just the same as any other bowl to put together and turn.
I suggest you cut a few segments and spacers first for one ring only, glue it up to check out how you are going to put it all together to get an idea.
An after thought is next time I do one I will use marine ply as it is a higher quality ply.
Good luck if you have ago