Hi Roger,
It’s based on Kians post, which is this one
Youll find how he made the 15S1P, i did it similar.
Note, you do need to have copper tabs, or at least one side of the tab needs to be copper for soldering. So you can logically structure the packs.
Instead of soldering, you can also just drill 3 tiny holes in the tabs, and screw them together nice and tight.