Staples work too. Remove just before you reach them so they don't deflect the sewing machine needle. Depending on what I'm working with, I prefer to glue with contact cement, next option, leather tape or double sided tape, next staples, next poke a single hole every so often and tie together with thread. Don't like the time it takes to tie though. On pre-punched kits, I would tie them together to align all the parts, then of course hand stitch or lace after.
Tom