This is a quick and simple hack, using the parts that I had at hand to make a shield for the Adafruit Feather boards for providing power for them conveniently.
The Feather boards have a battery charging circuit on them, and you can buy LiPo batteries to plug into them. However, there is no power switch, and the battery just dangles there on its wires, just asking for trouble. If you try to just tape it to the back of the board, you are risking a short, since the battery's outside is metal. If you leave it dangling, you risk tearing off the wires. And on top of that, the battery connector that I have is a really tight fit for that socket, and it's hard to disconnect and re-connect it.
So I sat down, and made this simple shield. It takes a LiPo battery in the form factor of an AAA battery -- but don't be deceived, it's still a 3.7V LiPo. I used some scrap bits of headers to prevent the battery from moving inside, which really makes the thing look bad, but I don't care. If you like, you could make it look much better.