All that is left is to join the case halves.
Remember to remove any protective masking tape you applied earlier. Place the case top on the case bottom whilst guiding the button wiring into the cavity under the buttons. Take care not to trap any wires.
Use the four M4 screws to close the case. Again, don’t force anything. It is easy to strip threads in aluminium with too much enthusiasm on the end of an Allen key.
As a last task, check that nothing is left that ought to be inside the case, and nothing is rattling inside the case that ought not be in there!
This is how it should look once you’ve completed the assembly.