After the battery is out, we're presented with a plastic cover with all the phone's information (Model No., Serial No etc)

Notice the 4 Philips screw-heads in each of the four corners. Those need to go off.

After unscrewing, you might notice that the cover doesn't easily go off. Four clips are holding the back cover onto the front cover.

Use a Spudger and unclip the sides of the cover. It shouldn't put up much resistance