something else you can do is solder the wires between the cells and not on them. that distributes the heat across the tab and doesn’t get any one cell too hot. Still need to keep the total soldering time down to a few seconds though.
Very obvoius
Although, I still think there’s a chance for some possible heat damage with this method… but I’m sure it would be fine to be honest. These 18650’s are pretty hardy cells actually…