Scimmy, you can also solder the cells. I've used stainless steel flux and low temperature solder to do this sort of job and it works like a charm, and at last I cover the solder jobs and their surroundings with homemade rosin flux to protect from oxidation; this last step is not strictly necessary, but without it the acidic flux treatment will cause some oxidation on the surface of the cells (step recommended if you aim for a long lifespan battery pack with upkeep).
Or you can buy the cells with pre-welded nickel tabs, this way you can solder them with standard solder and soldering iron.
A hair off-topic but related, both Liitokala and Vbatty are just rewrapping cells they buy from a chinese OEM or original equipment manufacturer, pretty sure. The actual original manufacturer rating very likely is 6 Ah per cell, so you can get this if your cells are top bin; and while I do not discard the possibility of higher capacities and energy densities, the 7 Ah rating in these rewraps is definitively a lie.
In fact, even the very own top OEM manufacturers lie with their capacity ratings, even if only a tiny tiny bit, and it's a shame. I cannot agree with this. An “everyone lies” is no excuse or argument to keep on lieing. Manufacturers could both believe in being trustworthy, showing trustworthy product ratings, and successful at the same time. And offering a trustworthy product rating is as easy as ensuring that your rating is a guaranteed minimum that all cells or batteries match or meet.