In the bowl of a stand mixer fitted with the dough hook attachment, beat bread flour, semolina flour, and 2 cups water at low speed until just combined, about 1 minute. Sprinkle yeast on top of dough and let it sit for 10 minutes.
Add salt, and beat on low speed until combined. Increase mixer speed to medium-high, and beat until dough becomes smooth and elastic, anywhere from 2 to 5 minutes. The dough should be smooth and uniform, but it will be sticky. Now reduce mixer speed to low, and with the mixer running, add the olive oil in a slow steady stream. Beat until incorporated, 2 minutes or a little longer. It will not look “right” to you, but it’s fine. Just make sure the oil is not pooling at the bottom of the mixing bowl. The dough will look wet and not totally uniform. That’s okay.
Now spray a large mixing bowl with cooking spray and tip the dough into the bowl. Cover the top and let rise in a warm, draft-free area until doubled in size, 1 ½ to 2 hours.
Preheat oven to 400 F. Line a jelly-roll pan (10” by 15”) with parchment paper. Turn the dough out onto the prepared pan and use your fingers to stretch it evenly to the edges. Dimple the dough liberally with your fingertips. Sprinkle with sea salt. Bake until golden brown, 18 to 20 minutes. Immediately brush with olive oil when it comes out of the oven. Let cool at least until you can comfortably handle it with your bare hands, or all the way to room temperature.