I posted this under Multiple Use Items but since I use several pieces of gear to create something else, I thought it should be posted here as well.
I've never been willing to carry the weight of a Thermrest chair but have often been envious of friends that were sitting around in them and had tried unsuccessfully on several occasions to make one using my pack. I finally got it!
You need a pack with internal frame, 6’ long 1” wide webbing strap (longer for big guys) with a buckle, half (5 folding sections) of a Zrest and a scrap of Tyvek. I always carry at least one strap for it’s many uses; I have gone to an air mattress and half of my old Zrest is carried as it makes a good sitting pad and back up short sleeping pad (air mattress failure) and the scrap of Tyvek is the door mat and sitting pad sheet. Thread the strap up just over half way across the back of your pack (maybe tighten your compression straps, etc. to find a suitable spot). Double 4 of the pad sections of the Zrest and have the 5th one project forward when you sit on the doubled sections. Sit on the pad with the pack behind you and the 5th section under your thighs. Bring the ends of the strap around your hips and hook the strap between your legs. Adjust the strap under your thighs (hip bones is the location that work best for me) and move the foot of the pack closer or further away from your backside for the angle adjustment. The Tyvek keeps the pack and Zrest out of the dirt and protects the Zrest from tearing as you wiggle, etc.