The easiest way to take off the MobilePal SlimFit battery case (including MP-IP6-3100 and MP-IP6P-4000) is to start from the lower part of the battery case. There is a small opening between the frame and the body of the battery case above the Lightning charging port. You can take off the frame more easily by gently pulling up the frame with fingernail or a paper clip from the opening at bottom part of frame (see the picture below), and then slide iPhone 6 out.
