If it is Hobbs 80/20 quilt batt, BOTH sides are fusible. I lay my sandwich out on the floor and dry iron the front working from the center out. I flip over the entire sandwich and dry iron the back from the center out. You can peel up the edge and re-iron as needed to make sure the back is wrinkle free. I spend the most time getting the back perfect because that is the side you can't see while machine quilting. I put a few safety pins around the edge so I don't accidentally peel up a corner as I move the quilt around while machine quilting.