Turn the device upside-down and insert a pry tool between the two case pieces.

On the left side just below the buttons there's a delicate ribbon cable that's part of the screen assembly and may be severed by a pry tool. (This is shown in the third photo, it's where the tool is pointing.) Regardless of where you start, stay clear of this area!

If you are having trouble getting an initial gap to pry from, run the flat edge of the pry tool along the front-to-back plate seam until it slips into a gap. You can also flex the device slightly and work a tool into one of the lower corners, which have a lot of empty space behind them rather than fragile components.

Looking at the back face, another safe place to start is on the right side just below the page turn buttons. (Note the green arrow in the board photo, which is rotated 90 degrees counter-clockwise.) The tool goes between the lower button and the hinge cover slot. If there isn't a slot there, you're on the wrong side!

Do not attempt to pry directly on the page turning buttons.

Work the pry tool around the edge of the case, releasing the 18 clips. Don't insert your tool too far, or you may damage components near the edges of the device. The clips are all in the outer edge of the backplate anyway. Note that the clip above the power switch is bigger and stronger than the rest.

Pull the rear cover off. The remaining two clips near the center of the back are surprisingly strong.

When reinstalling the back cover, slide the bottom edge into place first, and then press up the sides and along the top until all the clips snap into place.