The stairs were built using very simple method,
(1) cut all steps to size on a tool with a stop
(2) take a file and sand the depression in the middle
(3) take your stringers (the side pieces) and take a piece of strip wood the size that you want in between the steps and mark one side
(4) lay it flat and glue one side of the steps on your layout lines
(5) adjust steps for spacing while the glue is still wet
(6) apply glue to tops of steps AFTER the one side has dried lay down and attach the second side I used two heavy pieces of metal on either side to keep them clamped.
I hope thats as clear as mud for everyone
if not feel free to ask more questions I'll try to answer to the best of my ability. Thanks Pat