Make the Noodles:

In a large bowl, mix the flour and salt. Gradually add water and knead to form a dough. The dough should be smooth and elastic.
Cover the dough with a damp cloth and let it rest for at least 30 minutes.
After resting, divide the dough into several pieces. Roll each piece into a flat, wide noodle (about 1/4 inch thick). Apply a thin layer of oil to each noodle, sprinkle with a little salt, and set aside.

Prepare the Topping:

Heat vegetable oil in a small saucepan. Add minced garlic and green onions, frying until fragrant but not browned. Turn off the heat.
Add Chinese black vinegar, light soy sauce, dark soy sauce, chili oil, ground Sichuan peppercorns, sugar, and a pinch of salt to the oil mixture. Mix well.

Cook the Noodles:

Bring a large pot of water to a boil. Cook the noodles until they float to the surface and are tender but still chewy, about 2-3 minutes.
Drain the noodles and rinse under cold water to stop the cooking process.

Assemble the Dish:

Place the noodles in a bowl. Pour the hot oil topping over the noodles. Add any additional toppings like blanched greens, cucumber, or protein if desired.

Serve:

Mix everything well so that the noodles are fully coated with the sauce. Serve immediately.