I'm designing a simple PCB for GPS signal control. The frequency is below 5Hz, supply voltage is 9V and converted to 5V. This print will be screwed in a plastic housing with four M3 mounting holes at the corner which can be see in the picture. I have tried to route most of the trace on the Top signal layer.
My question is:
Is it a good idea to pour the entire bottom layer as GND? Or it can be on the Top layer too?
Should I connect the GND pour with the mounting holes? I saw a term called Chassis Grounding which makes use of screw for external grounding connection. I don't really understand this technique clearly, so I would like to have some advice on it.