Lay the iOpener over the plastic tab to loosen the adhesive. Let the bag sit on the device for approximately 90 seconds before attempting to open the panel.
Use a metal spudger to carefully pry near the Lightning connector and under all parts of the front panel assembly: the front glass/digitizer, the LCD display and the metal midframe.
The adhesive under the metal midframe/display assembly is quite strong and the components are fragile, so go slowly and gently. Make sure you do not bend the LCD screen.
Remove the volume rocker from the gasket and rear case.
During reassembly, use the pointed end of a spudger to fold the rubber gasket down away from the side of the case. Slip the volume rocker back into its recess and resettle the gasket.