My question is. How do you hold it while turning? Do you glue on a block, jaws in a recessed hole, or something I missing.[/QUOTE]
One way to use those blocks is to first decide which side is going to be the bowl side, start between centers with the inside of the bowl towards the tailstock. Rough turn it and start the interior of the bowl, but cutting only deep enough to form a tenon for the chuck and get the general shape.
Now you can turn the piece around and securely shape the outside (underside) how you want and then cut the recess to turn it around and finish turn the inside of the bowl.
For me, I don't like the recess very deep so once you turn the piece around for the last time you need to remember to take light cuts and take your time with it.