1. Press and hold vol down and power, when the screen flickers, release buttons and quickly press all 3 side buttons (power, vol up, vol down)
2. Plug in the wall charger (not usb)
3. Use vol down to highlight the SBF Flash Option
4. Use vol up to select it
5. Press and hold the power button for about 3 seconds then release.
Now the phone should power down completely after a couple seconds and begin charging (you should see the battery charging icon). If it doesn't work the first time just keep trying, took me a couple tries before it started charging but it worked. It also helps to boot into the stock recovery and do a factory reset first. It works though.