The Torges seat is pretty comfortable and allows you to sit upright against a tree(proper posture).
I wrap the seat and one of those round foam heat-a-seat things with the rope (side-to side, not like in the pics). Slip the tag end trough the loops around the wraps and strap it to my backpack.
I made mine with 1/2" plywood and some old wader neoprene glued on with outdoor adhesive (wrapped over the front and back).
1" stainless hex-screws for added grip on the tree.
Sealed the edges with Titebond 3 wood glue, then a quick spray paint camo on the bottom.
You could probably wrap up one of those lumbar support mesh things as well.
I made an extra for my father-in-law...and he repeatedly says to me "Have I told you that that seat is the cat's meow?" or the like.