I have written a detailed tutorial on how I use TouchTerrain to convert satellite imagery into a 3D model that can be carved with my MPCNC (or any CNC machine). And then how to carve and finish it. Here is an example of my latest work, including a resin ocean. It has a lot of practical details that should be enough to get you started if you have never done anything like this, or accelerate your progress if you have tried and gotten less than satisfactory results. I have been doing these for about 6 years now, and things got much easier since TouchTerrain came out!
I am also making a YouTube video to go with it, so please offer your comments and suggestions for improvements either here or as a comment on Instructables.