To make the dough: In a large mixing bowl, combine the water and active starter, mixing well with your hands. Add half the flour (eyeballed is fine) and mix well; a few lumps are OK. It will be the consistency of pancake batter. Cover and let sit at room temperature for 30 minutes. After 30 minutes, add the remaining flour and salt. Mix until uniform using your hands. The dough will be quite sticky at this stage; bring it together in the center of the bowl, using a bowl scraper. Then cover and leave to rest for 1 hour at room temperature. After the first hour, stretch and fold the dough for 1 minute in the bowl using a bowl scraper or your hands, turning the bowl as you go so it folds from a different direction each time. Cover and rest 1 hour. Do this three more times. You’ll need a total of four sets of folds. After the last set of folds, cover the dough in the bowl and transfer to the fridge to ferment overnight, at least 10 hours and up to 14 hours. In the morning, generously oil a 2-inch (5-cm)-deep, 9 x 13-inch (23 x 33-cm) metal pan with 60 milliliters (1⁄4 cup) of olive oil, spreading it evenly across the bottom and sides of the pan. Gently transfer the dough to the pan using a bowl scraper and fold it over itself once, then, using your fingers, gently press it out to a rectangle shape, coming to about 2 inches (5 cm) from the edges of the pan. The oil should pool nicely in the corners and little divots on top of the dough. Cover and place in a warm spot for 1 hour. After 1 hour you should see some bubbles on top and the dough should have increased its volume by about half. Gently press the dough out further so it reaches the corners of the pan and, using your hands, dimple the surface of the dough. Finish it with another light drizzle of olive oil. Cover, place in a warm spot and proof for 1 hour, or until you see more bubbles forming on the surface. Heat the oven to 450F (232C) with a rack in the center. When hot, transfer to the oven. Bake until golden and bubbly, browning deeply in a few spots, 30 to 40 minutes depending on your oven. While it bakes, make the syrup: Combine the water with the honey in a small saucepan and bring to a simmer over medium-high heat. Turn off the heat and leave in the pot in a warm spot. When the focaccia is done, carefully remove it from the pan using tongs or a spatula and transfer to a resting rack to continue cooling. With a pastry brush, liberally paint the honey syrup all over the focaccia, giving it two coats. Sprinkle liberally with flaky salt. Cool another 20 minutes before slicing.