I've used a Nexus 6P for some time now, but after coming from a oneplus and samsung before that, I always preferred the back button located on the right. This option was built in with the one plus, but I never found an option for the Nexus 6P without resorting to rooting and mods, which was too much a hassle for me to do it.
However, I recently found a post on xda-developers (https://forum.xda-developers.com/pixel-xl/help/swap-recent-button-oreo-t3687721) which only required using adb and fastboot to swap them and man was that easy, so all credit goes to that user for making it this easy.
All you have to do is download and install adb, enable debugging mode on your phone and open a command prompt (on windows 10) and run the command:
settings put secure sysui_nav_bar "space,recent;home;back,space"
and voila, the back button is located on the right where I'm used to it.
Note: You need to authorize your phone first to be able to run adb shell. If you run adb devices in the prompt, a popup on your device will appear asking to authorize. Press allow and now you should be able to run it