The motherboard is held tightly in place by small, fragile plastic clips. Be very careful as you pry during the following procedure.

Use the flat end of a spudger or your fingernail to carefully bend the plastic clips around the motherboard to the side in order to free the motherboard.

Repeat this procedure for all plastic clips around the motherboard.

Note that there are also clips underneath the rubber pads covering the two side buttons.

Don't try to remove the motherboard all the way yet. It is still connected to the battery.