The top rear centre trim panel snaps off first - just put your fingers behind the top of it & pull, then after it unsnaps, lift up & out. (note: there are 3 clips - one each side & one centre)
The two panels behind each seat just unsnap also (4 clips-one in each corner)
Remove the centre armrest box at the rear of the console - there is a false floor inside, note the little slot at one end where you can lift the panel with a small flat screwdriver blade. Then unscrew the 4 philips screws & remove centre box.
The screws should now be exposed for the rear centre panel & you can also remove that.
If you need to remove the corner rear side trim panels, the passenger side is relatively easy: remove the leather sill trim pad (unsnap it) and then pull back the rubber door trim surround rubber. Then remove the Philips screws & remove the panel.
The driver's side is similar but with a couple of complications: to remove the leather sill trim, you first need to remove the fuel lever - it just pulls directly off the lever (towards front of car); if you have trouble, leverage it off with a large flat blade screwdriver.
The second complication is the hatch lever handle; it is secured behind the lever handle with a hitch clip. Wedge out the lever from the panel with a large flat blade & then remove the clip with a pair of needle-nose, or pry it off with a jeweler's screw-driver (be sure you don't lose it!. Then repeat as previous to remove it.
Curious - What do you need to access behind those panels for your nav install?