I have a front & rear dashcam (separate units) and for the front I tapped into the switches beneath the headlamp selector that has Tow, Trunk and something else that I can't remember.
Doing this is both easy and neat.
By opening the drivers door, you can see a triangular shaped panel left of the vent and parallel with the door. This pops off revealing lots of empty space plus the area behind the switches.
Remove the connector of the switches above to give yourself a little more cable to play with, tap into the +ve and you're good to go. From their your dashcam wire can run directly up the pillar then along the top of the windscreen under the liner and it's invisible until it pops out to your dashcam.
For the negative, that's easy too. After popping off the triangular shaped plastic, if you are looking into the hole, to the left is a nut that is bolted to the chassis. Just crimp a circular connector onto your wire, take nut off, slide connector over bolt, replace nut. Voila
Sorry, typing this while not with car and so cannot add pictures. If this description proves to be more confusing than helpful, I can add photos later in the week.