You sit on it, but it is not free-standing. It is not a stool as it has only two legs.
Thus, it is the Un-Chair.
Not want to be slavish, needing a porch perch for to watch the winter rains (should we be graced to have any),and ever keen to employ my stack of barrel staves, I opted for the two-legged chair, leaning fashion.
There is no plumb or square to a barrel stave: curved from top to bottom and the sides bulge/bevel, which makes the joinery a challenge.
Most of the parts, aside from the staves are maple scrap (except for the ply seat), and the seat is cantilevered out of mortise and tenon joints.
I had originally thought that the thing would simply lean against the porch wall, but could not did not solve the anti-skid property needed at the bottoms of the staves, and so opted for a sort of hanging cleat.