Cubecell Module minimal design

I have been playing around with the cubecell dev board, and have got my sketch working enough that I am ready to design a PCB to use the module instead of dev board.

What is the minimum design I need to make the module work?

The reference design for Arduino module appears to have a lot more going on than the AT version.
Can I upload an arduino sketch using the AT version, or do I need to do everything on the arduino reference design?

I am trying to keep my pcb as small as practical. I am happy to program with a 2nd arduino if that works.