After removing the back cover, SIM-card(s) and the SD-card, proceed to unscrew all 17 screws.

Removing these two warranty stickers will obviously void your warranty

Identical 16 Phillips screws

1 Torx screw. Use a T5 Torx screwdriver.

After removing the screws, insert a prying tool of your choice (preferably plastic) between the back cover and the front panel and pry the back cover loose.

Move around the phone with the spudger. You will hear clicks as you proceed detacting the clips around the phone. Four different parts should come off relatively easily. Once done, you will have the motherboard exposed.