Wash the English cucumbers thoroughly under cool water. Pat dry and slice into rounds or half-moons, about 1/4 inch thick.

Chop the peanuts and green onions finely. Add them to the bowl with the cucumbers, and optionally sprinkle in red pepper flakes. Gently toss to combine.

In a separate bowl, whisk together the peanut butter, maple syrup, and soy sauce. Gradually add cold water until the dressing is smooth and pourable. Stir in sriracha, rice vinegar, and sesame oil.

Pour the dressing over the cucumber mixture and toss gently to coat, ensuring all cucumbers are covered.

Transfer to a serving dish and garnish with sesame seeds and extra green onions if desired. Serve immediately or chill for 10-15 minutes.