Northvolt’s original factory in Skellefteå is near (well, ‘Arctic near’: 460 km along an existing rail line) Kiruna, one of the largest Iron mines in the world, so that’s one of the two material supply safe.
Industrial Sodium is made with electrolysis of sea salt; the factory is next to the Gulf of Bothany and has abundant (wind and hydro) power, so the other material supply is safe.
It wasn’t hard anywhere, but it’s straightforward in that particular case.