Work out what angle the handles should go in at. Not quite 90 degrees because of the slight curve from crossbar to where the handles go. Drill the holes. Test fit Mark up where the cuts are going to go to fit the saw blade. Cut them, had to widen the one for the pins with some needle files as my hacksaw blade wasn’t thick enough.
Quick test cut to make sure I’m not completely wasting my time, seems to work. Mostly at least, frame swings about way too easily so I'll have a think on how to sort that. - Turns out this was down to my stupid idea of adding brass wear points to the end of the handles, adding a couple of leather washers fixed the issue.