Remove back cover by fingernail easily.
Remove battery.
Remove these 12 screws and remove the back frame. Unlike iPhones, these screws are all the same length. The top part of the frame comes with the power button flex while the bottom part of the frame comes with loudspeaker.
Remove the black, shorter screw and pry up the power & volume button flex cover.
Carefully loosen the power/volume flex from its adhesive.
And finally, remove the flex.
Release the digitizer and LCD connectors. The two cameras are held slightly in the frame. Carefully remove the motherboard with cameras.
Remove rear camera from motherboard.
And next, remove front camera.
Remove signal cable.
Remove vibration motor.
Remove earpiece speaker.
Remove headphone jack.
First, loosen the screen flex from the adhesive on the plate. Then heat the screen edges to melt the adhesive sticker. Next, use the guitar picks and opening tools to cut the sticker.
At last, remove the LCD screen.
LG G3 teardown is done.
All info from: https://www.ifixit.com/Teardown/LG+G3+D855+Teardown/42288#s97693