In the bowl of a stand mixer fitted with a paddle attachment, stir together the flour, sugar, salt, and yeast. Add the water and mix to combine. Once the water is integrated, switch to the dough hook and knead until the dough is stretchy.

Remove the bowl from the mixer. Wet your hands and coax the dough into a ball. Coat it with a tablespoon of oil. Cover the bowl with a damp towel and let the dough rise until it has doubled in size, about an hour or so. Gently deflate the dough and fold it over itself a few times. Reshape it into a smooth ball and let it double in size a second time (this can be done overnight in the refrigerator. If you choose this route, let the dough return to room temperature for about 2 hours before proceeding with baking).

While the dough rises a second time, preheat the oven to 425°F. Grease an 18 x 13-inch rimmed baking sheet with the remaining 2 tablespoons of oil. Once the dough is finished its second rise, turn it out onto the prepared pan. Using your hands, stretch it out to the corners of the pan, making small holes with your fingertips as you stretch the dough. The holes will close during baking, but if you don’t make holes through to the bottom of the pan, the bread won’t have its characteristic craggy, pockmarked surface. If the dough is bouncing back too much, let it rest a few minutes and resume your stretching and prodding.

Arrange the marinated artichoke slices and red onion slivers on top of the focaccia, pressing them in firmly.

Let the focaccia rise again for 10 to 15 minutes, just until the dough starts to curve up around the artichokes and onions.

Bake until the top is nicely burnished and a peek at the bottom shows an even brown exterior, 20 to 23 minutes. Remove from the oven and let the focaccia cool in the pan. Do let it cool to room temperature before slicing, to prevent it from becoming gummy inside.