Combine bread flour and salt in a large bowl. Make a well in the middle and pour in hot water. Mix together with a wooden spoon to form a shaggy dough.

Transfer dough onto a lightly floured work surface. Knead dough until sticky but relatively smooth and elastic, dusting with a minimal amount of flour if needed. Wrap in plastic wrap and let dough rest for 2 hours.

Mix vegetable oil, sesame oil, and flour together in a skillet over medium heat until starting to bubble, about 3 minutes. Cook for 1 minute more. Remove from heat and cool to room temperature.

Unwrap dough and cut in half. Roll out into a tube and press down with your fingers. Use a rolling pin to flatten dough into a rectangular shape about 1/8-inch thick, flipping over and dusting lightly with flour halfway through.

Paint surface of the dough with the oil mixture until just covered, leaving 1 inch of space on the edges. Sprinkle scallions on top. Roll dough up tightly to seal in the scallions, starting with the long side. Pull the opposite edge over the top once you have reached it.

Coil 1 end of the dough inward toward the middle; wrap the opposite end around the coil to finish, tucking the tip under the bottom. Dust the coil with flour and roll dough out into a pancake about 1/4-inch thick. Repeat with remaining dough, oil, and green onions to make the second pancake.

Heat vegetable oil in a cast iron skillet over high heat. Add 1 pancake; lower heat to medium. Cook until crispy and browned, about 4 minutes per side. Repeat with the other pancake. Cut into wedges.