Now you can assemble the head unit by connecting the 2 parts.
For head units without a TV:
Return the circuit board to its place. Now our controller is hidden underneath it. Make sure to route all the wires from the right side, as shown in the photo!
Place the head unit on something soft to avoid damaging the screen.
Connect both parts, but do not secure them yet! Pay attention to how the USB wires are routed. They should be routed through the hole as shown in the photo. They must not be pinched; otherwise, they may be damaged and will not work.
The rest of the wires are much easier. They are thin enough to fit under the cover comfortably. I routed the wires for the cameras to the left. But you can improvise if you find there is a better place for them.
For head units with a TV:
All the wires are already outside, on the back cover. Therefore, when connecting the parts of the head unit, there is no need to worry about how to route them.