Regarding how to access the board

① Slide the clamp card off.

The clamp card is held in place by double-sided tape to prevent it from shifting, but you can remove it by sliding it with a little force.

② Next, remove the screw and the switch part.

Since the switch part is not fixed by screws or other fasteners, it can be easily removed by pulling it or turning it upside down.

③ Remove the screw hidden under the clamp.

Slide the clamp upward and remove one screw located under the clamp.

④ Separate the handle part and the bellows part to access the circuit board.

By removing the two screws and the switch part mentioned above, you can disassemble it as shown below.
Again, if you are replacing the battery, please be careful about the battery polarity (positive and negative).
*It is safer to access the USB-Type C charging by removing the pommel.