I also posted this on EcoModder. Someone mentioned that larger cells are easier to work with. So, I posted what I found as far as making smaller cells such as teh 18650 into larger packs.
There seems to be more resources out there now to assemble 18650 cells into larger packs without fancy tools / welders.
These are the two that seem nice IMO.
Vruzend makes these interlocking pieces that can be assembled into whatever size and shape battery you want.
https://vruzend.com/
This guy sells these circuit boards that just pop in 18650 cells like most AA battery holders.
https://kit.com/jehu