Gently lift the cup away and peek inside without fully removing it. You should see the following:

A thin layer of tape holding a cable going from the boards to the NFC antenna in the outer shell piece.

Another thin layer of tape below it holding the headband cable and NC microphone cables to the mainboard.

Gently pry the layer of tape holding the NFC cable.

Once you've done that, it should have enough slack, and then you can open it like a book from the right side.