This year has been a learning year of how to make 12 or 16 seam centers lie flat.
I've experimented pressing all seams in the same direction and spinning the point, pressing all seams open and spinning or folding the point. Then a little birdie suggests to sew only to the center point - not past it. Sewing only to the point intersection definitely worked much better and was easier to spin the center seams. Note: be careful that you cannot see a hole in the center on the front side. This may happen with 6 or 8 seams and with 10, 12 or 16 seams it is highly unlikely.