Wash and prepare all vegetables: slice cucumbers, halve tomatoes, dice avocados, and thinly slice red onion.
In a small bowl or jar, whisk together olive oil, lemon juice, minced garlic, salt, black pepper, and red pepper flakes if using.
Place prepared vegetables in a large mixing bowl.
Pour dressing over vegetables and gently toss to combine, being careful not to mash the avocado.
Add chopped cilantro and give one final gentle mix.
Let the salad sit for 5-10 minutes to allow flavors to meld before serving.
Taste and adjust seasoning with additional salt or lemon juice if needed.
