Fleur de sel is the salt from the top of the pot when you heat salted water.
But what makes it different from the rest of the salt in the pot?
Seasoned Advice is a question and answer site for professional and amateur chefs. It only takes a minute to sign up.Sign up to join this community
I'm not 100% sure but I found this site that explains what fleur de sel is. It says that
Like other sea salts, fleur de sel is harvested by evaporating sea water. However, to harvest fleur de sel, workers gently skim the top layer of the sea salt from partially evaporated pools, before it sinks to the bottom again. These salt crystals are very fine, light, and delicate, and must be handled with care and exposed to minimal moisture, or they will clump again.
It looks like you are reproducing how fleur de sel is made, through boiling the water which is the equivalent to "evaporating sea water".
Unless you can distinguish it from other salts in a double blind randomized controlled trial I do not think that it is worth the trouble. Setting a trail up with a few friends is a lot of fun :)
There is an incorrect assumption in your question. Fleur de sel (flower of salt) is not salt collected from the top of a boiling pot of salted water. It's salt collected from evaporated ocean water. This is important and contributes to the following differences:
It's a specialty product. It's harvested by hand on nature's schedule. The sun is the heat source. Winds can disrupt the formation of the flowers. It's expensive.
Most importantly, I just tasted Maldon flaked salt, kosher salt, and fleur de sel back-to-back while writing this answer. They taste different. That's probably the most important thing to note.
Since the salt crystallizes in a manner that produces large flat flakes it makes it ideal for finishing a dish since it offers a small textural contrast while providing good salt coverage. Compared to coarse kosher salt it provides a small crunch and adds texture to the dish without being overwhelming it. It's also visible versus something like a fine grained table salt. It's a finishing salt though, so get some nice cheap fine grain salt for your regular day-to-day needs, and keep your fleur-de-sel in a small pinch pot to throw on finished dishes immediately before serving.