Carving the leaves around the edges, setting them in and grounding the background is quite time consuming. If my diameter is 24in (61cm) then I have over 6ft. (a bit under 2 metres) of edge to carve. But, hey, we carvers are persistent, if not patient!
There is no need to undercut; just make clean, sharp walls and junctions. Also, in parts, carve the ends of the leaves using full depth of the wood available. Both these approaches will save a lot of time.