Now that we have a case to work with, lets start with the screen. The screen is the best feature to add first because it will determine the space for each side of the case.
Create a new 110px x 140px canvas and insert the screen you want to appear. Paste this on top of the case and add the following layer styles:
Style: Outer Bevel
Technique: Chisel Hard
Depth: 121
Direction: Up
Size: 3
Soften: 0