This is fantastic, very useful stuff. I literally just finished writing a similar post:

https://www.stavros.io/posts/making-gsm-board/

Conor, can you detail how the assembly is done a bit? I've made a few boards with KiCAD but I have no idea how to go from bare PCB to assembled PCB, especially for such low cost as yours.

I went to PCBcart but counting all the items on my board was a hassle, and I got a cost of $38 per board for a run of ten, which sounds too expensive. Besides that, how do you even export the BOM from KiCAD? It doesn't come with a plugin by default.

A few details or a post on how to go from PCB design to assembled board would be very useful, at least to me.