How to Cut a Mesh - The Forest Style Tree Cutting

Hey unity answers, my question has to do with cutting a mesh, hopefully through code. I am creating a survival game and have been trying to get "The Forest" type tree cutting where it actually cuts into the mesh. Is there a way to do this through code, maybe with taking the mesh render values like vertices and all. One way I can think of is simply make multiple models for the tree. This would not be the preferred way because I do not have an artist. If this is the only way then is there any tutorials or something for me to do it in blender? Also how do I get the standard assets into blender? I will change the graphics once the game is completed but I want to prototype with the standard.