There are 11 stretch-release adhesives that secure the battery to the frame. Each adhesive strip has a black pull tab:

Six on the inside edge of the left battery cell

Five on the inside edge of the right battery cell

The remainder of the adhesive is located under the battery boards.

Use your fingernails or tweezers to peel each pull tab away from the edge of the battery.

Be careful not to deform or puncture the battery—especially if you're using tweezers.