The user must flash an older firmware version (often FW 6.3.1.0 or similar depending on the current exploit vector) using the fastboot oem update command or a specific flash tool. Amazon devices have anti-rollback features that must be bypassed.
You might encounter discussions about a hardware modification to unlock the bootloader by shorting a circuit on the tablet's motherboard.
: Installs Google Play Store, Google Play Services, and framework dependencies automatically.