We had the OSB boards cut by a CNC routing company [CNC Routing Cape Town]. They were given the exact tread and riser dimensions, and their computer controlled routing machine cut the boards in the zig-zag fashion required.
We then laminated these sections together using glue and screws to form 4 sets of stringers.
These stringers were then bracket fixed to ledger supports at the bottom....
.....and at the top of the stairway.
The stringers were evenly spaced over the 1m width of the stairway.
And finally we glued and nailed spruce plywood subfloor treads and risers to the stringers to complete the structure and create a base on which to lay the final floor finish. 8 LED footlights were also installed either side of the stairs. All in all, it is not as difficult as one might think it is to construct a staircase.