Lots of mock-ups are showing the Apple ID scanner under the screen that appears when needed. I doubt that this will be the case since the technology is not yet available that can place sensors directly below the screen. Instead, there will be a dedicated area at the bottom of the glass that will house the scanner while on the sides you will have the screen. This will be similar to how the phone looks on the top with the front camera and sensors, but taller. You will likely be able to place two of your most frequently used apps in the dock to the left and right of the scanner. This closely parallels Ming Chi Kuo's leaks about a dedicated function area at the very bottom of the screen.