A carved ring standing in front of an opening looks like the simplest thing on this table. It is the hardest to build, and the reason is grain.
Wood is strong along the fibre and weak across it. Cut a ring out of a single board and you get a shape in which the fibre runs correctly at the top and bottom of the circle, and completely across it at the two sides - so the ring has two built-in weak points opposite each other, and it will crack at one of them sooner or later.
So a ring is never cut from one board. It is built from segments, each cut so its own grain follows the arc it represents, joined end to end around the circle. Each joint sits where the next segment's grain can support it, and the joints are staggered against the ones in the layer behind so no two ever align.
Only once that blank is glued up and true is the carving started. The scrolls and flowers are worked around the ring continuously, crossing the segment joints as though they were not there - which they should not be, once the piece is finished.
The shell at the bottom is carved separately from thick stock and let into the ring, because a shell has depth the ring itself does not carry, and no ring segment could be made thick enough for it without ruining the section everywhere else.