Looks like you're good to go for the final assembly:
Screw in the Raspberry Pi and the USB extender to the Base. You might need to use some glue to put the switch in place.
Glue the screen assembly you've got earlier to the monitor box.
Glue two magnets in the holes on the front of the Base and the Keyboard. Be sure to orient them so they attract each other to close the lid instead of repelling.
Screw the Monitor box rear cap.