PSA: finally sewed my first real coptic stitch after 4 botched attempts, and the 5th try was a Tuesday night win
I used waxed linen thread instead of the cheap stuff I grabbed at Hobby Lobby, and the signatures sat flat for the first time. The trick was poking the holes with an awl through a folded paper template so they lined up on both sides. Any advice on keeping the kettle stitches tight when you get to the spine ends?