The SIM tray is located on the other side of the motherboard.
In order to get there, lifr all of the connectors attached to the board. (Camera, Screen, Power button, Network Coaxials, Fingerprint Sensor, Earspeaker, Prox/Light Sensors, Volume Buttons)
When Lifting board, be sure to lift at the top, as the Charge port is connected at the bottom. As you lift the board out, disconnect the Charge flex