A seam roll can be used to press areas that are hard to lay on a flat surface, like a sleeve. They also provide a curved surface for pressing seams without leaving imprints from the seam allowance. If you do not have a seam roll, roll up a newspaper or magazine and cover with a terry towel or insert in a wool sock.
Use a clapper to flatten seams after pressing. A clapper can reduce bulk and make fabric lay flat. Steam press the seam or area. Press the clapper over the area to seal in the heat and moisture. After about a minute, the fabric or seam will lay perfectly flat.