How to train roots to buttress

I have read a lot of articles on nebari or surface root growth and maintenance. However, I haven't come across a lot of material on how to train roots to buttress.

I have seen a lot of pretty amazing Bald Cypress bonsai with nice buttresses. I have also seen a couple of very large Tridents that buttress as well.

So, I want to experiment with a small Bald Cypress and grow it in the ground. Someone from my club told me that if I grow the cypress in a large plastic container (with the pot-base cut off) and plant it in the ground, then that should encourage buttressing. He said that when I am content with the trunk, then I should simply severe the roots escaping the bottom of the pot and gradually train it for smaller containers.

Any other tips or verification of the above technique would be great.