After reading a few recent articles on lightweight camping chairs, the reluctance to carry them, and the joy of sitting on them, I thought I would post my own preferred back-support method.
I use a framed backpack to which I attach two pieces of rope near the top. My backpack has a handle conveniently located for this purpose, but almost everyone's pack has something. Then I tie those two strands of rope around a tree, or I use my hiking pole and a tent stake to create tension. Then I just plop down on the ground, buckle myself in with the waist strap and lean back. It's perfect for reading a book or journaling. The only trouble is just getting it right so that the rope doesn't dig into your neck or shoulders.