Oldtool.
Thank you.
Yes, that's right. It began with a piece of wood around 8 inches x 8 inches.  3/4 to 1 inch thick.  The rings were cut on a 45deg angle.  the important thing to remember is to allow enough for the base. Too many rings mean nothing left for the Base.    The rings are stacked and glued and sanded to make sure everything lines up neatly.
The sanded and completed rings are then glued to the base. This way the inside of bowl doesn't need any more sanding.
but would still be possible to light sand by hand between coats of finish.
I will try to remember to give more detail in the future. 
Regards ....Cliff.