Im in the process of building an O-27 layout.
O-27 was chosen for 3 reasons. 1) I already have some track and a train, 2) The limited space available. 3) low cost.
I watched some movies about building O-scale layouts with lots of tips and tricks.
One of them was to use foam board for the road bed and bevel the sides at a 45deg angle.
To make O-27 look better, I found some spray-paint called "flec-stone" to paint the cut foam road bed to look like rock.
I also printed out an image of track with ties and affixed it to the road bed under the track.
Here is a picture of the result on my 1st attempt. I think i need to bevel the edges more (30deg?) and use thinner foam. (1/4").