Earlier today I was ready to scrap the base for this project - despite the insane amount of time I had spent laying individual bricks for the road. At this point I'm feeling a bit better about it... but I'm still not happy.
In addition to the flagstone wall I have added earth to the bulk of the base. I'll colour that with some pigments and add bits of ground cover after everything else is finished.
But as it stands at this moment there's a 50/50 chance that the base could be scrapped altogether.