With trees behind, consider using the rock to put in arcing tiers of seat height rock walls. Dry stack is a real skill - 18" thick /seat depth . . look on the internet for tips for how to fit them together to do that . . use the trees themselves as a backdrop and between the slab and the trees do a pergola wall between .. thick posts or tree poles on the stone bases, a sort of natural limb screen wall and cantilevered trellis . . .possibly a bundle of boulders buried 1/3 deep to make a 1/2 circle on the front edge of the concrete slab . . with a dug out fire pit in the center of this.

Bruce's Garden · More Info

This sort of back wall will do it .. though you may have to scale up . . . posts every 12' min . . .if you have trees at two spots with a clearing between, you can connect them visually this way .. diy plans for these sorts of elements can be found on the internet

We have been checking the internet, but lots of them look as if an army of landscape artists worked on it, not a 17 year old scout and his friends! I like these ideas, both within their reach, hopefully we'll have more to choose from. I like these too, because of the distance to the project is going to put a crimp in time, especially because he works too.