1: Pour 500 ml sea water into a pan on the lowest heat possible.
2: As the water evaporates, crystals of salt will start to appear on the surface...
3: ...until the water has entirely disappeared.
4: Scrape the bottom of the pan and you will have your "fleur de sel" salt flakes.
Remarks
It's worth noting that all types of salt have the same basic taste (unless of course there is something added). What "fleur se sel" offers is a different texture, rather than taste, and it is for scattering over the top of dishes rather than mixing in, as this adds nothing different from normal salt.