I first resawed down the middle, a piece of black gum burl approximately 4 inches thick (the finished piece is 8 X 4 1/2 X 4 1/4 inches tall). I then turned the pieces separately between centers in the same fashion as a natural edge bowl. I made sure the interior of the oyster would book match when glued together. Once the two halfs were completely turned and sanded, I placed them on a 4 inch table top belt sander (cheapo Delta model) at half the angle I desired the oyster to be opened. When a sufficient surface was attained at the rear of the opening to glue the two halfs together, I test glued them with just a bit of thin CA to make sure the fit was good, and that the jewelry dish was stable when standing on its own. This is important because you can make it somewhat top heavy toward the back if the angle is too wide. Once I was satisfied with the stability and the overall look of the piece, I glued it up with medium CA and allowed it to firmly set.
This next step may sound a bit crazy, but I put the glued up shell in the mircowave to completely dry it. I zapped it real good. Though you can't tell it in the pix, there is a slight texture on the surface from the microwaving and a small amount of warping at the outter edge that gives an authentic oyster shell texture to the overall look of the piece. Just one of those things that happens by accident but still rewards the intended look. I did the final finish by sanding it with 220, 400 and wipe on poly with steel wool between coats.
It isn't necessary to use burl for this particular piece. If you have a bandsaw, you can shape the form of an oyster or perhaps a clam (Shell Oil sign) and go through the same process. It's simply up to your imagination. I just happened to have this piece on hand and saw the design just laying there on the floor.
At the risk of sounding a bit over the top "artsy", I have learned that when doing free form turning, you shouldn't force the wood to give you what you intend it to be, but simply allow it to show you what was there from the onset. I'm presently working on a mushroom box from some of the same black gum burl that will have a lid shaped like a mushroom when viewed from overhead. I didn't plan it, it was just there.
Hope this didn't bore you, and thanks for giving me an opportunity to share.
Larry