Once you’re done sucking your thumbs or outsourcing that little exercise and having someone else suck it for you. You can take out the battery. Note that if you had the device on, it will turn off once the cover is cleanly off.
Now if you’re like me, you’ll notice that unless you’ve got tweezers for fingers, you really can’t grip the battery to pull it out. Then you’ll start pushing into it because you think it’s spring loaded (it’s not). Then you’ll suck your sore thumbs while thinking of all the reasons you hate life. Then if you’re lucky enough, you’ll scratch your head while holding said phone and the battery will fall off. That’s right, all it takes to remove the battery is simple gravity.
The lesson as always is: I’m an idiot. But you probably knew that already.