If you watch Jennie she sets the seam (sometimes) and then rolls back the fabric with the iron. I don't believe this is ironing because you're not stretching the fabric and pushing too hard on it. You will be able to see the difference once you learn how hard to use your iron. It's all trial and error and as long as my pieces fit I don't stress. You will know when you're not doing it right because the pieces won't fit together!