There’s a guy named Jehu Garcia in California who’s made it his mission to recycle laptop and other batteries in the United States instead of sending them back to China.
One of his ongoing projects is building DIY power walls (similar to the commercial ones made by Tesla at a premium price) using these reclaimed batteries and modular PCBs and commercial battery holders.
This is a lot easier than soldering the cells together with nickel strips and making your own brass buss bars.
Here’s his tutorial on putting together the battery packs, including how to match cells, and even build the ribbon cables for the battery management system monitoring.