This past spring, I created a root on rock with some Limber Pine seedlings I acquired. Here are a few pics of the rock before planting.
The lava rock had a nice bowl shape and it would have been fine to utilize that bowl to plant in. I have always been a fan of Masaniko Kimura's Japanese White Pine planting on a convex stone slab. I chose to do my planting in a similar fashion. I used 3 small Limber Pines to complete the planting. The next photo is of the current back of the planting.
This photo is of the chosen front. 
The negative is that you can't see the tree's base due to a lip on the rock. Personally, I liked the interesting underside of the rock that gives the impression of a cave to me. As the planting matures, the other side may become more attractive.
The lava rock had a nice bowl shape and it would have been fine to utilize that bowl to plant in. I have always been a fan of Masaniko Kimura's Japanese White Pine planting on a convex stone slab. I chose to do my planting in a similar fashion. I used 3 small Limber Pines to complete the planting. The next photo is of the current back of the planting. This photo is of the chosen front. The negative is that you can't see the tree's base due to a lip on the rock. Personally, I liked the interesting underside of the rock that gives the impression of a cave to me. As the planting matures, the other side may become more attractive.
. Beginning pictures brought to mind Master Kimuras composition even before you mentioned
