Use vertical grain wood that has good strength. I used Cherry, turns, sands easy and has good vertical strength. The piece is 2 1/2" inches square by14" long.
Use a roughing Gouge to turn the square wood into a round dowel. After the wood is round I used a
100mm jaw to hold the piece.
To create the Goblet I used an 1 7/8 " Forstner Bit, It is easier than trying to hollow small diameter end grain. The Goblet is 2" deep with 1/16" sidewall. Starting at this point you should turn and final sand in small segments.
The Stem will be turned to 1/4" so, it will be fragile. The way to support the Goblet is to stuff a couple paper towels into the Goblet and use a live center with a flat profile. Advance the live center until it starts to turning, then slowly advance until the Goblet is firm between the centers. Too much pressure will cause a deflection in the stem and it will break, too loose and the Goblet will wobble while you are turning.
Form the Goblet to the beginning to the stem, finish sand to your final grit. As I make the rings I use tape to keep them out of my way.
To begin the Captive Rings I use a parting tool to create a bead (for lack of better word) and gently round the edges.
Starting with the Ring Tool, work from both sides and make the ring round and under cut the back. Work both sides evenly and slowly.
I used two rings on the Goblet; made three rings but did not like the first one. Start the stem slowly finishing only about 1" at a time and finish, vibration is you enemy.
Goblet finished and ready to part off.
Oops! snagged the parting tool and broke the base.
Turn a new base.
The new base has a 3/4" hole and the stem is also 3/4" with a slight taper, .73" to .78". I wanted it to fit tight and have room for the glue. It takes some effort to get the stem in straight, use the paper towels and the tailstock to press the stem into the base, gently
Completed base. When I made the new base I turned a small dovetail in the bottom so I could hold the base with pin jaws.
Completed project. I took the time to turn a top for the Goblet but did not photograph it, sorry.