The simplest way to create the illusion of a three-dimensional tree is to ensure adequate back branches. These should be angled so that they are visible from the front,like the branch indicated by the white arrow above.Additional depth is created, especially in multi trunk trees, by planting in a diagonal fashion as shown by the red arrow above.

Another important refinement is to ensure that side branches angle slightly forward, like those shown by the white arrows below.In combination with the apex leaning slightly forward, the tree seems to be bowing and holding out its arms in welcome.