All of the waste material has been removed around the tree and moon elements. Keeping it to an even depth is the trickiest part. Getting into all of the small nooks and crannies where the branches meet requires using extremely small tools. For that reason, the depth can be no more than about 1/4 inch.
As you can see in the close-up, the sides of the tree are not perfectly squared. When the tops of the branches are rounded, the tree will appear to emerge from the body of the Gaia.