Add the flour and salt to the bowl of a food processor and pulse for 15 seconds. With the motor running, stream in 3/4 cup of boiling water. Continue processing until the dough balls up around the blade. If the dough does not come together, add more boiling water, 1 tablespoon at a time, until the dough forms.
Lightly flour your work surface then turn out the dough. Knead it for 30 seconds then cover it with a damp towel and let it rest at room temperature for 30 minutes.
Divide the dough into 4 equal pieces.
Working with one piece of dough at a time (and keeping the remaining pieces covered with a damp towel), roll it out into a 8-inch circle. Brush it lightly with sesame oil then sprinkle it with scallions. Roll the dough up into a log then shape it into a coil, tucking the end under the bottom of the coil. Flatten the coil slightly with your hand then roll it out again into a 7-inch circle. Set the pancake aside under the damp cloth while you repeat the rolling and filling process with the remaining pieces of dough.
Add 1 tablespoon vegetable oil to a medium skillet set over medium-low heat. Once the oil is hot, add one pancake and cook it, turning frequently to prevent the scallions from burning, until it is golden brown and crispy on both sides, about 5 minutes total. Transfer the pancake to a plate or wire rack then repeat the cooking process with the remaining vegetable oil and pancakes.
Cut the scallion pancakes into wedges and serve them with the dipping sauce (recipe follows).