Prep the cucumbers: Peel the cucumbers. Cut them into quarters, lengthwise. (If the seeds are bitter, scrape out the seeds and discard.) Cut the cucumbers again, crosswise, into 1/2-inch thick pieces. Toss the salad: Place cucumbers into a serving bowl. Sprinkle with salt. Toss with sesame oil, seasoned rice vinegar, basil (if using), and chili flakes. Sprinkle with toasted sesame seeds if using.