Step 1: In a large bowl, whisk together the flour and salt. Gradually pour in the hot water, stirring with a spoon until a shaggy dough forms. Add 1 tablespoon of sesame oil and knead briefly on a lightly floured surface for about 5 minutes, until smooth and elastic. Cover with a damp cloth and let rest for 20 minutes.
Step 2: While the dough rests, prepare the dipping sauce: In a small bowl, combine soy sauce, rice vinegar, grated ginger, sesame oil, and sugar. Stir until the sugar dissolves. Add red pepper flakes if desired. Set aside.
Step 3: Divide the rested dough into 8-10 equal pieces. On a lightly floured surface, roll each piece into a very thin rectangle (about 8×4 inches).
Step 4: Brush the surface of each rectangle with a thin layer of neutral oil. Sprinkle generously with sliced green onions.
Step 5: Roll the dough tightly from one of the long ends into a log.
Step 6: Coil the log into a spiral shape, tucking the end underneath. Gently flatten the spiral with your palm.
Step 7: Using a rolling pin, carefully roll each spiral into a flat pancake, about 6-7 inches in diameter. Try not to let the green onions tear through the dough too much.
Step 8: Heat 1-2 tablespoons of neutral oil in a large non-stick skillet or cast-iron pan over medium heat.
Step 9: Place 1-2 pancakes in the hot skillet (do not overcrowd). Cook for 3-5 minutes per side, or until golden brown and crispy. Repeat with remaining pancakes, adding more oil as needed.
Step 10: Remove cooked pancakes from the skillet and place on a wire rack lined with paper towels to drain excess oil. Cut into wedges or strips and serve immediately with the ginger-soy dipping sauce.