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.
Solar stills work by putting something that can be as simple as a sheet of clear plastic over a hole in the ground, and putting a bowl under the peak of the sheet. A greenhouse with a brackish pool and a way to collect the precipitation would be a scaled up version.
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.