Heres my first go at a base. Still have to paint the runway but I did the grass on both sides. For doing it cold turkey with a ruler and my naked eye, I think the measurements and such are ok. For the terrain I did a layer of brown ballast then a sprinkled fine turf over it for that patchy look. I might try to enhance it more, what a messy job this was!
Still have to fill in some spots with paint which the ballast missed, mostly along the wall edge.