Slide the card out from under the middle cell group.

Leave the card that's underneath the left group in place for now.

Slide the plastic card underneath the far right battery cell group to slice through the adhesive holding it to the case.

Wiggle the card from side to side as you insert it under the battery cells to fully separate all adhesive holding them in place.

Leave the plastic card temporarily underneath the right cell group to prevent it from re-adhering while you continue.