Here is a picture of the footprint I made for Fusion 360 (since unfortunately there was no support from Seeed on getting the footprint). But the footprint I made SHOULD work just fine, right? I am using the GND pin so I only need the BAT+ pad soldered. I squirted in flux and then soldered the pad to the plated through hole. But… no dice! the connection didn’t work at all in one PCB and the second PCB I had printed worked spottily.
You might be right, the spacing between the XIAO and the board might be too much. I soldered the pins first and then the pad second. Maybe I should have done it the other way around.