Wash and chop the cucumbers into bite-sized peices and place them in a large serving bowl.
Add the sliced shallot, crumbled feta, fresh dill, chives, basil, and diced avocado, if using.
In a separate bowl, whisk together the olive oil, lemon juice, red wine vinegar, garlic, salt, and black pepper until well combined.
Pour the dressing over the salad and gently toss until everything is evenly coated.
Taste and adjust the seasoning with additional salt, pepper, or lemon juice if desired.
Serve immediately, or chill for 15 to 20 minutes before serving for even fresher flavour.