Using the edge of the board as a guide, I trimmed up the felt . This is why it is important to leave at least a 1/2" of felt around each side, because anything less will be hard to cut. A good buffer on the sides allows you to hold onto something while trimming and you can pull it away as it separates. Make sure you're using a sharp blade so you won't tear it. Here, you can see the trimmed edge (bottom left) and three more untrimmed edges.
The next step was to draw out the roads with a black Sharpie. I measured out where the roads would join the edge of the board to make sure that the boards are interchangeable. I centered each road at 16" from an edge, and made the roads 3" wide. Then, I free handed the roads on the felt and cut them out with my knife to just the outside of the line. I'm not very good at free handing, so any goofiness in the roads can be fixed when I lay down the plaster surface for the roads. Finally, once the roads are cut out, pull up the felt, keeping your hand on the side that won't be removed. Again, go back with your glue and spot fix anywhere the felt is coming off.
My final step for the night was to apply black spray paint to the pine bark I would be using for the cliffs. I laid out the bark in the design I'd planned, then moved them to my painting surface and sprayed them. I will likely have to wait till Sunday to work on the cliff and roads, but the bark will be attached with a hot glue gun. I'm looking forward to this step the most!