Slice the cucumbers into thin rounds, approximately ⅛-inch thick. For best results, use a mandoline slicer if available.
Place sliced cucumbers in a large bowl and sprinkle lightly with salt. Let sit for about 15 minutes to draw out excess moisture.
Gently pat the cucumber slices with paper towels to remove excess moisture.
Add the freshly chopped dill and sliced red onion (if using) over the prepared cucumbers.
In a separate medium bowl, whisk together the sour cream, white vinegar, sugar, lemon juice (if using), minced garlic (if using), salt, and freshly ground black pepper until smooth.
Pour the creamy dressing over the cucumbers and dill, then toss gently to coat each cucumber slice evenly.
Cover the bowl and refrigerate the salad for at least 30 minutes before serving to allow flavors to meld.
Just before serving, give the salad a gentle stir and sprinkle with fresh chives if desired.
