Cheers for steering me in the right direction.
For anyone wondering I got this working with a TP4056 by wiring the 5v and GND pins out to the VIN and GND respectively on the TP4056 then wiring the OUT+ side to a simple on/off switch and then from there to the 3v3 on the board, and likewise the OUT- to the GND pin on the Xaio. B+ and B- go to your battery connector. Makes for a really handy “safe” rechargeable lipo circuit on one USB port. The on/off switch is optional and the battery will still charge when the Xaio is plugged in via USB. You can also accomplish this without the 5v to the VIN on the TP4056 if you don’t mind using a different port for charging/programming, personally, I just removed the USB port on the TP4056 to save space in my enclosure.