Here’s what I do to keep mine from curling while I’m working on it. Initially I tie all my strands together with a large, loose knot and pin that knot to the arm of my sofa. When I have about 1 inch knotted, I secure it a second time with another safety pin closer to the end where I’m working. Every few inches I adjust the pins so that the second one is always close to where I’m knotting and the other is an inch or two above. This holds the bracelet flat and steady and will make the process much easier for you.

Of course, not everyone attaches their work to the sofa. Some people use tape (but I find that can ruin the floss) or a clip board. You’ll have to find what works for you, but if you secure the bracelet in two places as you work, you shouldn’t have so much trouble.

If the bracelet curls when you’re finished, try ironing it with the steam setting of your iron, or wetting it and allowing it to dry while held flat.
References :