Wow - more a challenge than a commission, but hen, aren’t they all.  

A fellow member of the IWCS used to make segmented bowls.  He cut accurate
segments of a circle and glued up within a PTFE ring (circle of yellow gas main)

I would attempt something similar  to construct an open cone void.  Even using
only 6 or 8 segments, you are able to cut the blanks so as to form the rough
interior shape, then refine on the lathe.  You may need some form of inserted
centre to provide stability whilst roughing off the first part of the material.
30 degree angles for the essentially coopered construction are no harder than 45
for a corner, and you then join up in pairs for octagons, or threes for a
hexagon, so you can check and refine the mating joints as you complete each
gluing.

As for the curve itself, can you gain access to an existing one and make a
template?  otherwise it will be t’internet.  I have no ideas.  I might suggest a
hard lacquer finish somewhat against my principles as the final finish.


Enjoy!  


Richard Wilson
locked down under grey skies in Northumberland.