California live oak

I was given a California live oak grown (non-bonsai person)  from acorn in a large pot. It has great bark and nabari.  I would like to begin transferring it every other year into smaller and smaller pot. Working toward bonsai pot. I have been told they are very sensitive to root trimming. Any suggestions how I can go from a giant 5 gallon root bound pot eventually to a bonsai pot with limited root pruning, and not give killing this potentially gorgeous tree?

Can you please share a picture? 

The big word in bonsai is patience. If it doesn't like root trimming then cut just a little bit every other year and move it to a slightly smaller pot.

Maybe instead of buying a new ceramic pot, make a wooden box and shrink it slightly. 

If you are in California there is probably a club near you and probably somebody there has experience with the species. If not, some internet searching might find a club with contact information.