Notes:

I like to get downloads finished first!

Google Factory Images:

Stable - https://developers.google.com/android/images
Beta - https://developer.android.com/preview/download-712.html#top

Pure Nexus Rom (Custom Rom):
XDA URL - https://forum.xda-developers.com/pixel-xl/development/rom-pure-nexus-substratum-fi-wifi-t3533539
Official URL - https://www.androidfilehost.com/?w=files&flid=138513

TWRP (TeamWinRecoveryProject):
XDA - https://forum.xda-developers.com/pixel-xl/development/twrp-alpha1-pixel-devices-t3500312
Official URL - https://dl.twrp.me/marlin/

ROOT (SuperSU):
Official URL - http://www.supersu.com/download

Elemental Kernel (Custom Kernel):
XDA - https://forum.xda-developers.com/pixel-xl/development/kernel-elementalx-pxl-0-02-t3487072
Official URL - http://elementalx.org/devices/pixel/

Unified Android Toolkit (Great for Flashing Factory Images):

Official URL - https://skipsoft.net/download/uat-v156/

Minimal ADB Fastboot (Flashing TWRP Temporarily to boot):

Official URL - https://www.androidfilehost.com/?fid=745425885120698566

Installation Instructions:
# Make sure on latest stock FW

# Flash TWRP

Run the following:

adb reboot bootloader 

fastboot oem unlock 

fastboot boot twrp.img

# Wipe Data Factory Reset

# Install Rom

Note: If needed, flash specific Vendor IMG in TWRP

adb push purenexus_marlin-7.1.1-20170317-OFFICIAL.zip /sdcard/
adb push vendor.img /sdcard/

# Reboot into OS

# Flash TWRP - USE ALPHA1

# Install TWRP - USE RC1

# Install SuperSU (Make sure you INSTALL SuperSU from ALPHA version, not RC1)

# Install Kernel

# Reboot into OS, profit! 

# Download SuperSU & RootChecker from PlayStore to confirm working as expected

# Backup

# Customize!