First, let me say that this arrangement of trees, as well as their development really creates the impression of a forest in nature.
If this was a single tree (of this same quality) planted in a pot, it would be grossly over-potted. The fact that it is a forest doesn't lessen the perception. The first thing I notice is that this forest sits on a (near-)perfectly flat uniform mound of soil/muck/forest floor. Additional separation and interest could be given to the planting with some diversity of height (of soil in the planting) and possibly shape near the edges of the slab.
Having only worked with forests of this quality and age a handful of times, I understand that there are difficulties in rearranging the layout or altering too much what its planted in. I'd expect over a few years/repottings some diversity of height/thickness/slope could be added without sacrificing the health of the plant (either by taking off the top, or shaving away the bottom??).
Would that be an improvement in anyone else's mind? I've seen forests purchased from big names that are "potted" similarly and always wondered about it.
(But, to be clear, this is (another) very fine tree. Thanks for sharing.)
