Make the Dressing: In a small bowl, combine the minced shallot, fish sauce, lime juice, soy sauce, garlic, pepper flakes, and sugar; whisk to blend. Taste for seasonings and refrigerate until serving time.
Assemble the Salad: In a medium serving bowl, combine the cucumbers, green onions, and cilantro. Cover and refrigerate until serving time.
Serve: Toss the salad with the dressing and chopped peanuts. Garnish servings with more chopped peanuts if desired. Enjoy!