Remove the tape holding the battery in place.

Gently lift the battery from the bottom using a plastic opening tool.

You may have to apply heat to melt the glue holding the battery in place.

Do not completely remove the battery yet

You can now disconnect the flex cable holding the PCB board place. Gently open the gates using tweezers or a plastic opening tool and use tweezers to slide the flex cable out.

Now that it's separated, remove and set aside the PCB board.