Make sure all the cables and connectors are clear of the board, and use the flat edge of a spudger to gently lift the bottom of the motherboard.

The narrow part of the motherboard is very fragile. If it starts to bend when you lift, stop and make sure there isn't anything holding the board down. The board should lift up without any resistance.

Holding the wide part of the motherboard near the SIM card slot, carefully slide the board toward the bottom of the phone while lifting it out of the phone.

Remove the motherboard.

Try to keep the phone flat with the battery facing up after you remove the motherboard, as the front-facing camera can fall out of the phone case very easily.

When reinstalling the motherboard, move all the cables and connectors out of the way of the board and make sure all connectors are aligned with their respective sockets.