A BEAUTIFUL flask, I used to make weed pot similar to this, and a friend used to macrame (knotting string) ropes for them, The method I used was different, I carved half of the bottle shape out of wood, and mounted it on a stout board, I also cut out a piece of ply the same outline as the wooden forme, but 3mm clear all round, I then would staple a piece of soaking wet leather to it, and clamped the leather over the former, after a couple of days in the press, the shape was fixed, I would glue both halves together and hand stitch, I don't think I managed to make one as nice as yours though!