Here is a good YouTube from Bjorn on creating a clump style bonsai.https://www.youtube.com/watch?v=XsaMNDTA65M&feature=youtu.be
I tried it with some larch -- they may have been too large already as they had small lower branching, but I guess I'll find out. :) Also have an order in for some aspen seedlings, so I will try it with those when they arrive.