On a 2" x 12" plank, use a framing square to the measure the dimensions of the riser and the tread (Image 1).
Slide a locking nut on at each measurement and tighten down (Image 2).
Lay the framing square on the 2" x 12" and mark the dimension (Image 3).
Align the framing square so that the line for the top of the second step just meets the line for the bottom of the first step.
Mark the steps out along the length of the 2" x 12."
Use a circular saw to cut along the lines (Image 4). Cut all the treads in one direction, then change the angle and cut all the risers. Avoid over cutting the corner.
Finish corner cut with a handsaw (Image 5).
Work back and forth between angles for a nice sharp corner.
Neaten the corner -- if necessary -- using the handsaw.
Depending on the number of steps needed, chop the 2" X 12" stringer to length on the miter saw.
Place the first stringer in place against the front edge of the first landing.
Screw the riser portion into place using #16 framing nails in a nail gun, toenailing them at an angle through the riser into the landing.
Use 3" deck screws to attach the tread portion to the floor.
Also attach the stringer to the legs of the third landing.
Scribe a line with a level across the landing and attach the second stringer in same manner.
For additional support, attach another 2" x 4" ledger under the stringers.
Angle the top of the ledger on the table saw so that it fits tightly between the stringers and the landing.
Snug it in below the stringer and screw it into place.
Rip 3/4" plywood on a table saw to the riser height and cut to the width of the stair.
Nail a riser on each upright face of the stringers – all the way down.
Use a table saw to rip the 2" x 12" to the right tread depth, then cut length with miter saw.
Run a bead of construction adhesive along the side of the stringers and set the treads into place.
Nail treads in place using #8 framing nails (Image 1).
Nail boards atop landings (Image 2).
Next, add winder landings to make a 90-degree turn. First, build three 30 degree angled boxes out of 2" x 12"s ripped to the riser height.
Miter corners by marking angle on wood with a T-bevel, then start miter cuts on each side with circular saw.
Use a reciprocating saw to finish cutting through 2" x 12" at angle.
Nail triangular boxes together with #16 framing nails.
Run a bead of construction adhesive along edges of third landing where first winder landing will sit.
Toenail it into position.
Add second and third winder landings in the same way.
Cut triangular treads to fit the tops of the winder landings out of 2" x 12"s.
Where the tread is wider than 12", join two pieces together with a cleat on the back made out of 3/4" plywood screwed into place (Image 3).
Use glue and nails to attach the winder landing treads into place.