In the following steps you will be releasing the clips holding the phone's cases together. However, the back case is also secured with an adhesive pad. After separating the clips you will use an iOpener to allow the case to fully open. Do not attempt to fully open the phone before loosening the adhesive.
Insert a plastic opening tool into the seam between the front and rear covers near the SIM card slot.
Slide the plastic opening tool along the seam toward the upper corner.
Run the opening tool along the seam around all four sides, separating the remaining clips holding the cover on.
The plastic on the front cover is thinner near the buttons, and the buttons may move around. Go slowly to avoid damaging the buttons or the front cover.
Do not push the opening tool deep into phone, or you may damage internal components.
Starting from the SIM slot side, carefully peel the back cover off of the phone.
The back cover is very flexible, but you don't want to damage any internal components by being too hasty.
There is a chance that the NFC coil may remain stubbornly adhered to the back cover. If that's the case, stop peeling the cover and reapply a heated iOpener to the back cover.
Do not separate the back cover entirely; it is still connected to the phone by the camera flash cable.
The flash cable is attached on the power/volume button side of the phone.
This doesn't address the antenna stuck on (but separate) from the battery. It's easy enough to see in the pictures, but it doesn't come off easily in one piece. I think mine still works, but definitely needs addressing.