• To dissolve the yeast, combine the warm water and 2 tablespoons of the sugar in the bowl of a stand mixer fitted with the whisk attachment. Allow to foam for 5 to 10 minutes. Whisk in the remaining 6 tablespoons sugar, 4 tablespoons vegetable oil, honey, and 3 eggs on medium speed until combined.
• Change to the dough hook. Add 512 cup flour and the salt to the bowl and knead for 3 to 4 minutes, starting on low and gradually increasing to medium speed, until a smooth, elastic dough forms. (Your dough should be tacky but not sticky. If it's too sticky, add a few tablespoons of flour at a time until it's tacky.) Transfer to a lightly floured work surface and knead by hand for 3 to 5 minutes, or until a very smooth ball forms, dusting with flour as needed. (Alternatively, if you make this dough entirely by hand, after incorporating the flour, it will take about 10 minutes to knead on a clean work surface.) Grease the remaining 2 tablespoons of vegetable oil into a medium bowl and your hands, then add the dough ball and gently turn to coat. Set aside in a warm place, covered with plastic wrap or a kitchen towel, until doubled in size, 112 to 2 hours.
• Divide the dough into 6 equal pieces on a clean work surface. Roll each into an 18-inch-long rope that is slightly thicker in the center and thinner at both ends. Lay out all of the ropes vertically, then pinch together the tops of each rope to seal, tucking the sealed end under itself slightly.
• Cross the two outer ropes over each other to swap places, crossing the rope from the right under the rope from the left. Take the farthest rope on the right and cross it to the center (with 3 ropes on the left of it and 2 ropes on the right). Then, cross the second rope from the left all the way to the far right. Now, move the farthest rope to the left to the center (with 2 ropes on the left of it and 3 ropes on the right). Cross the second rope from the right all the way to the far left. Repeat until there are no more ropes to braid, then pinch the ends and tuck them under the challah's end. (Instructions are provided below.) Transfer the challah to a parchment-lined half sheet pan on a diagonal, using your hands.
• Brush the challah liberally with the remaining egg. Allow the challah to rise again, uncovered, for about 1 hour, or until it has doubled in volume.
• Preheat the oven to 350 degrees Fahrenheit.
• Brush the challah once more with the remaining beaten egg, then top with the seeds and a generous pinch of flaky salt.
• Bake for 35 to 40 minutes, rotating the pan halfway through, until the challah is golden brown and has reached an internal temperature of 190°F. Remove from oven and set aside to cool completely before slicing. Serve the challah on the same day it is baked.

TO BRAID

• Lay out all of the ropes vertically, then pinch together the tops of each rope to seal, tucking the sealed end under itself slightly.
• Cross the two outer ropes over each other to swap places, crossing the rope from the right under the rope from the left.
• Take the farthest rope on the right and cross it to the center (with 3 ropes on the left of it and 2 ropes on the right).
• Cross the second rope from the left all the way to the far right.
• Move the farthest rope to the left to the center.
• Cross the second rope from the right all the way to the far left.
• Rep step 3 until all of the dough has been braided, then pinch the ends to seal and tuck the sealed end under.