Be careful with the small blue capacitors indicated by the orange box. There are many of these capacitors in the device.

Slowly lift the backside cover.

Both sides lift up the same way, but the motherboard is under one side and the battery is under the other.

Detach the four cables connected to the cover by pinching the connector clips and pulling the cables out:

Three cables on the motherboard side.

Two red cables with white connectors and one white cable with a white connector.

One yellow cable with a black connector on the battery side.

After detachment, you should be able to completely remove the backside cover.