The rollout has been slow for the newest Android 5.1 update, and devices under carriers still have to wait for the official build for them to tweak, and then release it as an over the air download. However, Google has already released official factory images for a possible Nexus 5 and Nexus 6 update to Lollipop 5.1 that can be achieved through flashing. 

The new build, which Google dubbed as the LM471, is officially available for download on their developer page. The site also contains flashing instructions for those who cannot wait for an official over the air update. However, sites which reported on the update such as International Business Times warn users that updating the device through flashing is meant only for middle to heavy Android users, which have fairly decent background when it comes to the mobile operating system. Nonetheless, there are step by step instructions on how to flash the Nexus 5 and Nexus 6 models to update the devices to Lollipop 5.1. 

One of the first things for users to check is the battery of the device, which should have at least 80 percent charge as the update might take a lot longer than when doing it over the air. Also, users should make a back-up of their data and settings. The correct USB drivers should also be installed on the computer, and that the phone is rooted with either CWM or TWRP recovery installed. The bootloader should also be left unlocked. 

The new Android Lollipop 5.1 update brings support for multiple SIMs and also allows HD voice calls across all platforms, and will also have a Device Protection feature. This security option will tie the device with a user's Google account along with its steps verification process to prevent unwanted access. 

For those that would wish to update their Nexus 5 and Nexus 6 devices without waiting for carrier-specified builds over the air, the flashing instructions and necessary image build downloads are available in the Google developer page.