I typically make my hills out of Styrofoam or mesh, covered with a layer of plaster. I apply a layer of grass and in some places, bushes, over that before adding trees.
I previously had a small disaster when drilling a hole to insert a tree, so I now only ever use a bradawl to make the hole for the tree. This is pretty easy unless one is going into solid wood, in which case drilling would be OK.
Some trees come with roots, and others with just a trunk. I recently used a bunch of second hand trees and they had root stands. I cut these off first.
Don't throw away the roots, they can be used to simulate tree stumps.
I then snip off any extraneous bits of the tree, remove any debris and old glue as may be needed, especially with second hand trees.
I pick a spot for the tree and gently make a vertical hole using the awl. I make it only as big as the trunk of the tree to be planted.
If your ground is well vegetated, one can easily lose track of the hole, so I hold a bottle of school glue in the other hand while making the hole so that I can add a spot of glue in the hole right away.
I then put down the awl and glue, and pick up the tree and a spoon of vegetation. I tap a small amount of flocking onto the blob of glue.
and then insert the tree trunk into the hole. Keep the tree vertical.
Once one gets the rhythm, they go in pretty fast!
Some trees that are made from wire, have shiny tips where the metal has been cut, so I place a bit of green paint on them.
I try to place them in clumps and mix species somewhat
