This chair design is old. Some say it dates back to the the mid 1700's with Mountain Men roaming the US. Some call it a Viking chair and claim it is a Medieval design. For certain it popped up in Boy Scout camps in the US in the early 20th century. Leave a comment about the oldest you've seen!
Regardless of who did what where or when they are still extremely comfortable, affordable, durable and can be used anywhere. My wife has owned one for the past 20 years. We have a few now. They store flat in a 45x12x4 inch space. They have followed us from a very small apartment, to garden parties at our house, into the mountains and down by the sea. They are always the first seats taken at any of our get togethers. They are more comfortable than any other any other outdoor chair we have - and honestly more comfortable than most of our "indoor" chairs. For that reason they have been our living room, camping and outdoor companions for the entirety of our married life. You might get one or two seasons out of a cloth folding chair - but this $8 investment will last you decades.
This design only requires one 2x12x8 board - typically used for load bearing headers and decking band boards. No nails or glue is required. Only a few basic tools are necessary.
You will need one board about 12 inches wide and 8 feet long. Sorry my metric friends. This is all in feet and inches. This cost me $8 at the big box home store.
Straight line tool of some kind at least 3 feet long
Drill with large drill bit
We need to cut off one 48 inch board. This will be the back board. Cut and set it to the side.
I've included a grid paper graph of what we are cutting. Each square is 1 inch. Grey shows the cuts. Maybe one day I'll get around to using sketchup.
**Edit: User GeeDeeKay hooked us up with a great PDF version of the plans.**
With the back board set aside we now turn to the other one. It needs to be cut 45 inches long.
Mark a 12 inch line from one end of the butt board. This will mark the seat. On that line mark two inches in from either side. Move down 33 inches and make marks at 2 inches in as well. Use your long straight edge to connect the 2 inch lines.
Basically we are cutting off 2 2x33 slices of the butt board.
Use a circular saw for what you can and finish the cuts with a hand saw.
Find the back board you set aside. Measure up from one end to 11 inches. This will be the bottom of our slot.
I cheated here.
Once you have your slot hole marked drill a hold to drop in your jig saw blade. This could be done several different ways. It is better to have the hole slightly larger than smaller.
Time for a test fit. If it fits - great! If it does not trim a little more out of the slot.
I like to trim off 1 inch corners off the head board and the seat.
It would also be appropriate to paint, stain or protect the lumber however you see fit for whatever you are using if for.
This chair easily stores flat under a bed, under a couch, behind a door and tucks away easily for camping.