I know sea salt is produced by filling up big pools and letting the sun do its thing, but capturing the water is challenging.

Although come to think of it, existing greenhouse technology would work, "just" fill a greenhouse with a layer of water or let it mist, then capture the precipitation off the roof. I'm pretty sure it needs a way to passively cool the thing though. I'm also sure there's a lot of factors why this wouldn't work, probably due to scalability compared to alternatives like reverse osmosis, land use, etc.