We’ve written about Concrete Canvas before, but I thought this was an interesting application. This stuff is pretty much exactly what it sounds like—a fabric impregnated with cement (though I doubt the cloth is actually canvas).
Here designer Florian Schmid has wrapped the dry material around a demountable wooden form, sewn it at the edges with what looks like Paracord, applied water, and then removed the form after the cement has set. His website, linked below, shows off a chair, a bench, and three different stools made with the same method. Concrete Canvas is manufactured in the UK, and it looks like they are willing to supply small “man-portable” quantities.