Wash and thoroughly dry the cucumbers.
Place the cucumbers on a sturdy cutting board.
Gently smash each cucumber with the flat side of a large knife, a rolling pin, or the bottom of a heavy cup until it begins to split.
Cut the smashed cucumbers into chunky bite-size pieces.
Place the cucumber pieces in a colander or mixing bowl. Let them rest for 10 minutes, then drain away any released liquid.
Transfer the drained cucumbers to a large mixing bowl.
Add the thinly sliced red onion and green onions.
Add the crispy chili oil, soy sauce, toasted sesame oil, and sesame seeds.
Toss gently until all the cucumber pieces are coated.
Let the salad rest for 5 to 10 minutes.
Taste and adjust with a little more soy sauce or chili crisp only if needed.
Serve immediately or chill briefly before serving.