Using a standard electrical box for mounting RLC-420

I have purchased a RLC-420 and am wondering the best way to mount it. I would like to use a standard electrical box for ease of wire routing and an over all better finished look to the installation. But I am not sure what size (or shape) of box is best.

Any suggestions? What is the consensus as to best way to mount the camera and not have wires hanging around?

Thanks

Please kindly refer to the follow pic:
length
The length of your box should longer than 12.5cm. The minimum of the size should be 12.5*8*6cm.
All above only for reference.