Step 1: materials
You will need a strip of aluminum, mine was some scrap about 1/8" thick. I chose aluminum because it is easy to work with when cutting and filing.
You will need a power inverter. I got mine as a present so I don't know what it cost. luckily it had pop out plugs because I could not find cool ones at the hardware store. It also had a 5 volt usb plug which I thought would be cool to use.
All vehicles are different but you will need tools to get behind the dashboard plus whatever you are mounting the plugs to.
You will need wire and connectors to attach to the battery and the from the hidden inverter to the plugs. Be sure to use appropriate gauges for what current load you are expecting.
You will also need some inline fuses and a 12 volt extension plug. The one I got had two outlets side by side.
I used a drill, an angle grinder, a jigsaw some sandpaper and some files.
2 small bolts and nuts to mount the panel.