Cut the cucumbers in half lengthwise, then scoop out the seeds with a spoon.
Slice thinly (a mandoline is best for this), then toss with the salt and put in a colander; let drain (over a bowl or in the sink) for 10 to 20 minutes.
Rinse, drain, and wring dry in a towel.
Use immediately or wrap in plastic and refrigerate for up to a day.
In step 2, after drying, toss the cucumbers or other vegetables with 2 teaspoons rice vinegar, 1/2 teaspoon dark sesame oil, 1 tablespoon soy sauce, and 1 teaspoon mirin.