Yes you could do that, but there is a really good chance you wouldn't be able to achieve a suitable seam/seal in your bottle. If you're going for something really off the wall (like a face on one side and a yeti on the other) then yeah, that's the way to do it.
If you're just doing a normal one, it's much easier to sew it first.
Stan,
the images seem to have been lost, but here's the pinned article: http://leatherworker.net/forum/index.php?showtopic=3084