Place the sliced cucumbers in a mixing bowl and toss with ¼ teaspoon of salt. Let sit for about 30 minutes. If a lot of liquid is released from the cucumbers, you can drain the excess liquid. We only had a little liquid with the seeded English cucumbers and did not have to drain.
While the cucumbers are resting, whisk together the olive oil, vinegar, onion powder, sugar, and salt in a small bowl.
Add the fresh dill and chives to the cucumbers and pour dressing over the cucumbers and stir to combine—season with fresh ground black pepper.
Cover and chill for at least 2 hours before serving, stirring it a few times.
The cucumbers can be served cold or at room temperature.