Pry the seam between the screen and the case on all four sides with a large plastic opening tool until the plastic case comes off.

Lift the device off of the case and flip over the device so that it sits screen side down.

The device is now free from the plastic casing.

The power and/or volume buttons may fall out at this point. There is no problem with this; however, be sure to remember to reinstall them when reassembling the device.