I am making a 6 inch tall fieldstone bed edge around a tree. The one tree is a birch and it is solid root in the proposed area. Should I do a base, or with fieldstone at this height is it not that critical. I have another bed to do, but the ground seems a bit more cooperative, if i can whats the ideal base for installing fieldstone at this height. Im new to this, forgive me but Im a college student doing a job for my boss.