Wash and dry the cucumbers. Slice them into thin rounds and place them in a large mixing bowl.
In a small jar with a tight-fitting lid, combine the peanut butter, soy sauce, rice vinegar, honey, garlic, lime juice, chili flakes, sesame seeds, and salt. Screw on the lid and shake vigorously until the dressing is smooth and creamy.
Pour the dressing over the sliced cucumbers. Add most of the chopped peanuts and cilantro, reserving a little for garnish. Gently toss everything together until the cucumbers are well coated.
Transfer the salad to a serving plate or bowl. Sprinkle the remaining chopped peanuts and cilantro on top. Serve immediately for the best crunch, or chill in the fridge for 10–15 minutes.