Mix the flour and ½ teaspoon salt in a large bowl using chopsticks or a wooden spoon. Bring ½ cup water to a boil, then pour it into the bowl. Mix until the flour is evenly moistened and has formed large pebbles, then stir in ¼ cup cold water. Continue mixing until the dough starts gathering in large clumps. Turn the dough out onto a lightly floured surface and knead until a smooth, tacky dough forms. Pat the dough into a 1-inch-thick rectangle, cover loosely with plastic wrap on the work surface and let rest for 20 to 30 minutes.
Clean the work surface, then rub it with a thin layer of oil. Uncover the dough and roll it using a lightly oiled rolling pin into a 24-by-6-inch rectangle (about ⅛-inch thick). Drizzle the oil over the dough and rub it evenly to coat the surface. Sprinkle the dough evenly with the scallions and remaining 1 teaspoon salt.
Starting from one long side, roll up the dough tightly as you would a sleeping bag. Cut the long rope into 4 even pieces. Stuff in any scallions that may fall out at the edges and pinch the open ends and seams closed. Gently squeeze a piece to make it narrower and longer, then spiral it like a snail shell into tightly wound coil and tuck the end under the coil to seal. Repeat with the remaining pieces. Let rest for 20 to 30 minutes.
Gently press one coil flat with your palm, then gently roll it into a round 6 to 8 inches in diameter, depending on whether you prefer a thick or thin pancake. Repeat with the remaining coils.
To shallow-fry the pancakes, fill a medium skillet with oil to a depth of ¼ inch. Heat over medium heat until the oil is wavy, then carefully slip in a pancake. Fry, flipping occasionally to evenly brown, until crisp and golden brown, 5 to 7 minutes. To dry-fry the pancakes, heat a skillet over medium heat. Add a pancake and let sit until golden on the bottom, about 2 minutes. Flip, cover partially with a lid, and cook for 2 minutes more. Uncover and continue cooking, flipping the pancake every minute for even browning, until golden brown and no parts of the dough look translucent, 2 to 5 minutes more. To give a dry-fried pancake a little crispness, drizzle a little oil around the edges of the pan after uncovering and let it run under the pancake while it finishes cooking. Drain on paper towels. Serve hot.