I worked on the same end of the layout I was working on a couple of weeks ago and moved to the inside of the loop.
This structure has a large footprint so I needed more space than was at the top of the mountain.
I built up and leveled the building site and made a roadbed from cardboard. After that I used polyester batting for the landform under the plaster cloth. There is three layers of cloth for rigidity and strength. There will be some exposed rock like the level below and some grassy areas with a lot of spruce, fir, and pine.
The base is just a square of 1/2" plywood and a few other scraps I had laying about. I didn't have to cut one piece of wood.
You can see how the road winds down from the hillside and I may have this come out to the main road through a small tunnel underneath the ÖBB branch line and through what will be a rock wall. This is next to the interlock tower right after the main road crosses the tracks.