With a very thin spudger like the one shown gently pry the back cover away from the phone about half way down the long edge of the cover on either side.

When you have enough room, insert some plastic cards (such as plastic playing cards) and use them to cut through the glue around the bottom half of the rear cover.

Be careful not to pry around the top edge. If the patch antennas are damaged when the cover is removed be sure to replace them with new ones.

Slowly lift away the back cover, detaching the top edge last.