Here is my battery pack for my Onewheel for CnR.
For the batterys i choose 30x Sanyo/Panasonic NCR18650GA 3,6V - 3,7V 3500mAh in the configuration 10S3P (i choos a standard 10S BMS from ebay).
You also need XT60 male and female connectors, AWG14 cable, and basic things for soldering a battery pack.
Also you ned a sheet of 8mm thick EPDM rubber for the inside of the battery box (cut it to the hight of the 18650 retain frame and stick it on the frame on all sides - you must cut the 8mm EPDM sheet on one side to ~4mm to fit in the box, i choose the oppsite site of the BMS).