I have a ficus that I bought 2-3 years ago and it has been doing well
since it was placed in a pot that is 11" round and 8" deep. The plant
itself is about 26" high and has been growing rapidly indoors over the
last several weeks. The plant gets about 2-3 hours of early morning
sun. The climate outside is still harsh with plenty of snow on the
ground.

I would like prune the root as described he
http://www.bonsaisite.com/fatfig.html

i.e. remove all roots and then prune them so that I can create a
"tapering trunk and proper nebari". My questions are as follows:

- When is the best time to prune? I thought the pre-spring would be
good time as the plant would be dormant but it seems to be showing a
lot of growth (best in some time) and is far from dormant.

- Any other tips on performing this procedure?

The goal is to create a "large" ficus with a thick trunk and aerial
roots.

Thanks.