Hmm, well I did it backwards I guess. The very bottom of my sandwich is pieced as well, although I didn't notice any puckering with that part. It was completely flat when I taped it down. The batting in the middle is really thin, as it's Insul-bright, not actually batting, so you can actually see the seams from the "starburst" through it, although it is flat. It was the top (currently top of my sandwich as well) that was concerning me. The pictures show the puckering on the green turtle fabric and pink and black star fabric on my quilt top.