I’ve built a few modern looking mono stringer stairways and here’s a post on how it usually goes. The stairs I’ve done have had different ways of attaching the treads, but they’re all similar.
First I make a CAD model of what needs to be built. The mono stringer is a 5″ x 5″ x 1/4″ square tube with 1/4″ plate tread brackets welded to it.
Welding all the tread brackets to one side of the tube caused it to bow nearly 2″ in the middle! I bent the tube back straight by heating the other side to cherry red with an acetylene torch at every tread weld.
Next the stringer was bolted to the concrete slab and lagged to the wall.
The treads were attached to the tread brackets from the underside with countersunk Simpson Timber Screws.
Finally the railing was fabricated in sections that attach together with countersunk machine screws for a flush look.