Sometimes car seats are available free. It's a pity not to use a comfortable chair because the bottom of the chair is metal and will scratch a floor. To solve that problem, I make feet out of rope and silicone rubber for areas of the chair frame that contact the floor.
It's a little harder to lift one's self up off the floor, but while you are down the chairs are quite comfy.
One can even rock back in them, if you are not afraid of falling over backwards. If you are, you can put a sack or two of sand behind the chair to keep it from falling too far backward. Some chairs have backs that tilt down. Depending on where the balance points of the legs are, they can make great reclining chairs.
Step 1: The Chair Bottom
In an automobile, the seat slides forward and back on two tracks. I normally knock the tracks all the way back to move the legs more under my hips than under my legs. Keep in mind your body's center of gravity, which is around your hips.
You have to look for bolt holes, or other irregularities where you can run rope through to hold it in place, or ways to tie the rope to the frame. Rope is cheaper than silicone rubber, so it makes a good fill material. Wrap it tightly, with silicone rubber saturating it as you build it up. You will get a relatively cheap foot that stays in place and is tough, besides being soft and friendly to floors.
Step 2: Build the Feet
You can use white nylon rope, or yellow polyethylene rope. The yellow rope is springier and you sometimes have to clamp ends down with clothes pins in order to hold everything together until the rubber hardens up. Once the silicone sets up, you can release the loose ends trim them, and touch them up with a little more silicone.
The feet are kind of like turbans wound out of rope and saturated with silicone rubber.
Step 3: Falling Over Backwards
If you do fall over backwards, you won't fall far, and your back is protected by the chair. Your head is what you most have to be careful about. Try to not leave dangerous objects, such as table corners, where your head might hit them in an accident.
To prevent a full tip-over, I stack a couple sacks of sand behind the chair. They make a good chair stop, so I can lean back against them to use the chair like a recliner. A foot stool makes it complete.
Step 4: The Seat Cover
Instead of sewing seat covers, I just used some scrap cloth and safety pins. The cloth can always be returned to the cloth collection later for other projects if needed.
The cloth that covers the bottom tends to slip forward from sitting on it while leaning back. To keep it from slipping forward, I tie small objects such as marbles in bunched up pockets of cloth. The string that ties around their neck ties to contact points near the seat's back hinge points. That prevents the cloth that covers the bottom from sliding forward.
That's all there is to it. It's fairly quick, easy, and cheap. It's also very comfortable.