In a large bowl, combine 1 cup potato starch, salt, and vegetable oil. Gradually add the boiling water, a small amount at a time, stirring continuously until a soft, cohesive dough forms.

Transfer the dough to a work surface lightly dusted with potato starch. Knead the dough while it is still warm, adding more potato starch as needed, until it becomes smooth and elastic.

Roll out the dough to a thickness of approximately 1/8 inch. Using a pizza cutter or sharp knife, cut the dough into 1/4-inch wide strips to form noodles. Separate the noodles gently to prevent sticking.

Bring a large pot of lightly salted water to a boil. Prepare a bowl of cold water on the side. Add the noodles in batches to the boiling water and cook until they float, about 1 minute. Immediately transfer the cooked noodles to the bowl of cold water to stop the cooking process. Repeat until all noodles are cooked.

In a small mixing bowl, whisk together the oyster sauce, soy sauce, rice vinegar, ketchup, sesame oil, sugar, and Sriracha until well combined.

In a large skillet, heat the vegetable oil over medium-high heat. Add the minced garlic and sauté briefly for about 15 seconds, until fragrant. Sprinkle in the red pepper flakes and green onions, stirring quickly.

Add the drained noodles to the skillet, along with any residual water, if present. This helps prevent the garlic from burning. Pour in the prepared sauce and stir until the noodles are thoroughly coated and heated through, about 1 to 2 minutes.

Turn off the heat and stir in 1/4 cup of chopped fresh cilantro. Divide the noodles into serving bowls and garnish with additional cilantro and red pepper flakes, as desired. Serve immediately.