I made this chair with the help of Josh Hayden, when I had spare time after making an oak seated dining chair.
The back fits into a slot in the seat and is held in place by a through wedge underneath. The legs are firmly fixed, but not glued, so they can be removed. The through tenons allowed the legs to be adjusted slightly as they dried, if required. As well as retaining the bark on the legs the rear end of the seat still has the bark and the slightly asymetrical shape indicated by the piece of wood.
This seat was out of the same piece of oak as the dining chair I was making and both had splits that didn’t go completley through the wood, so the resin in the crack has maintained structural strength.