For those of you still having troubles finding the small plastic strip, here's another explanation.
Close the device, look straight above the camera button, where the chin and screen meet. There is a small plastic strip that can easily be shaved away at with an exacto/razor blade. If you still don't see where it is, continue looking in that area, and then press the screen where it always creaks and you can see the plastic piece rubbing up against the screen.
Easiest way to do it: find something to put between the chin and the screen so you can shave away at it while it is on something sturdy, such as a table.
Thanks again to the OP, the creaking was driving me nuts, now it's all fixed