I'm calling this a win. A tree canopy that can "flow" up or down hills. For a finished piece I'd flock the nail heads. I think I'll use string to mark the boundary of the forest on the ground and add some foliage or clutter to dress it up.
Instead of a rigid base like cardboard or foamcore, I used aluminum window screen. I covered it in clump foliage, attached with wood glue. Roofing nails are glued in point up to act as trunks. You could also use centrally placed wood cubes, as the screen is rigid enough.
A couple tips. Don't glue foliage too densely, it needs room to flex. Make sure your glue is absolutely dry. Overnight us best.
I expect clumps will pop off now and then, so travel with extra wood glue.
I will trim the screen off the edges and use shorter roofing nails next time.
