a. Install USB drivers and platform tools from android:
https://developer.android.com/sdk/index.html#Other / https://dl.google.com/android/installer_r24.4.1-windows.exe
Run it, then only select platform tools and Extra/USB drivers (uncheck others) for download/installation. Note the location.
Update ADB drivers via this hack (critical):
b. Unlock the OEM bootloader via http://www.skipsoft.net/?wpdmpro=uat-v144 SkipSoft toolkit. Awesome piece of work, that. Make sure its in ADB mode.
c. Download the ROM version you want from https://developers.google.com/android/nexus/images?hl=en#nakasi Unzip it (individual files within TAR) using 7-Zip into the platform-tools folder under the Android tools.
d. Navigate to platform-tools folder under SDK folder. Just run “flash-all.bat” script and you’ll be done in 2.5 minutes. Voila, no lag!