Building an 18650 battery pack!

I'm searching for suggestions on how to construct a 12V battery using 18650 cells. I've so far built a battery utilising Headway and Sinopoly prismatic cells. But I've stayed away from 18650s because they seem to be so difficult to find for a good price and decent quality. But I still want to make one.

This post is to get advice on the best course of action. I can solder even though I don't have a spot welder, but I'm not sure if it would be a wise idea for these cells. One thing I'm curious about is how many cells a regular 12V battery should have in series. If we were to use three AAA batteries, I was thinking of something around 60Ah.

With LiFePO4 we do 4s batteries but apparently with the lithium 18650s we do 3s?

Any thoughts on methods to hook these together would be appreciated. If it helps, the modem batteries I'm looking at are here

The specs are here

Thanks in advance!