Warm the vegetable oil in a small pan over medium heat until hot but not smoking. In a heatproof bowl, combine the chili flakes, garlic, green onions, sesame seeds, and sugar. Carefully pour the hot oil over the mixture, allowing it to sizzle. Stir in the soy sauce, water, and combine. Set the sauce aside.
Lightly oil a cutting board. Dip two-three rice paper sheets in cold water to soften them, then stack them together evenly. Place the stack on the oiled cutting board and brush the top with a little more oil. Cut the rice paper into strips, about 1 inch thick or as wide as you prefer. Toss the strips in the sauce to prevent sticking. Repeat this process with the remaining rice paper sheets.
Garnish the noodles with fresh cilantro and cucumber slices. Serve immediately for best results.
