Whisk together the flaxseed, flour, yeast, salt, and gluten in the bucket. Add the water and stir with a heavy wooden spoon. The dough is heavy (really, not kidding) and you might need to use your hands to incorporate the last bit of dry flour. (You can also do this in a heavy duty stand mixer with the paddle attachment.)
Cover the bucket (not airtight) and allow the dough to rest at room temperature until it rises and collapses, about 2 hours. Refrigerate for up to 10 days. (The dough works best when it’s had time to chill.)
Dust the surface of the chilled dough with flour. Cut off a 1-pound piece of dough (about the size of a large grapefruit). Dust it with more flour and quickly shape into a round ball or batard.* Ball: Stretch the surface of the dough on all four sides, rotating one-quarter turn as you go.* Batard: Shape into a ball then start elongating and stretching the dough until it has a diameter of about 3 inches. Roll the dough into a shape that tapers at the ends.
Place the shaped dough on a pizza peel or unrimmed cookie sheet dusted with flour or covered with parchment. Cover the dough loosely with plastic wrap and allow to rest for 90 minutes (40 minutes if using fresh unrefrigerated dough).
Thirty minutes before baking time, place baking stone on middle rack and preheat the oven to 450° F/230° C. Place the cast iron skillet or empty broiler pan on rack below. Just before baking, slash the dough in three diagonal 1/4-inch deep parallel cuts using the bread knife or lame. Slide dough directly onto the hot stone, or you can also slide the parchment onto the stone. Pour 1 cup tap water or ice cubes into the skillet or broiler pan and quickly close the door. Bake for 30 to 35 minutes, until richly browned and firm. Remove from the oven and allow to cool completely on a wire rack before slicing. (Trust me, waiting is the hardest part.)