When I do these slots I lay some removable drywall tape in place and start wailing away with the hacksaw. Well. Maybe it’s one stroke at a time. So it’s not really wailing. To do the opposing side of the crown, I take the same piece of tape and invert it so that I’m using a clean edge for a line of sight. Saves on tape that way. Next step is to run my little Bahco 6″ Barrette files through the cuts and show them who’s boss. Cool shit, huh.
All This By Hand