Jannick,
If you want the hackle to curve and sweep to the rear, the easiest way to achieve this is to tie it in on your side, tip to the rear, curved side out (towards yourself), and then start wrapping over the hook (away from yourself). This will make the fibers fall naturally towards the rear of the fly as you want it in a wet fly like this.
If you tie it in curved side in or wrap it the opposite way, it will have a tendency to stand our more perpendicular to the hook shank, which might be wanted sometimes (like in a Woolly Worm), but not in a more traditional wet fly.
Martin
