This is in reply to the matter of cutting paper square. I use scrap plywood and drive three finishing nails into it, two in line and one at the base. This forms a perfect right angle. Fold paper and put into signatures, place each signature under the hardboard and simply cut with a sharp scalpel, chisel, razor knife, etc.
All signatures are square to each other.
I have been doing this for years mainly for gilding. Then sew the text block together, this makes a 'rustic gilt' top edge or fore edge. The listserv for all the book arts.