Make the caramel. Preheat the oven to 325°F (160°C). Add the coconut sugar and water to a small saucepan. Cook over medium heat, stirring until the sugar dissolves. Once the mixture comes to a boil, stop stirring and let it simmer for 5 to 7 minutes, swirling the saucepan occasionally, until the temperature reaches 245-250°F on a candy thermometer or instant read thermometer (i.e. between the soft-ball and hard-ball stage). Note: You can reduce the heat slightly if the sugar starts to smell like it's burning.
Pour the caramel. Immediately pour the caramel into six ramekins (or one 8-inch round cake pan), tilting each ramekin to coat the bottom. Set aside and let the caramel firm up.
Heat the milk and sugar. In a saucepan over medium-low heat, combine the milk and coconut sugar. Heat until the sugar has completely dissolved and the milk is steaming but not boiling, about 4 to 5 minutes. Remove from the heat and let it cool for about 5 minutes.
Whisk the eggs. In a bowl, whisk together the eggs, vanilla, and salt, until creamy.
Make the custard. Slowly pour the warm milk into the eggs while whisking constantly. Once combined, strain the custard through a fine-mesh sieve into the prepared ramekins. Skim away any bubbles from the surface, then cover each ramekin with aluminum foil. Pro tip: I like to strain the custard into a 4-cup measuring cup. It's easier to pour from that, rather than the bowl, into the ramekins.
Bake the flan. Place the ramekins inside a large roasting pan or 9x13-inch casserole dish. Pour hot water into the roasting pan until it reaches halfway up the sides of the ramekins. Bake for 40 to 45 minutes, or until the edges are set but the center still jiggles slightly, when gently shaken. Note: The size and shape of your ramekin may affect cook time. The flan is done when it reaches 175°F (79°C) in the center on an instant read thermometer. Remove the ramekins from the water and let them cool to room temperature. Then, refrigerate them for at least 6 hours, though preferably overnight.
Serve. Run a thin knife around the edge of the ramekins. Dip each ramekin in a bowl of hot water for 10 to 15 seconds to loosen the flan from the ramekin. Invert each ramekin onto a rimmed serving plate and allow the caramel sauce to flow over the flan.