Cook the farro: Rinse farro under cool water. Add to a pot with 3 cups of salted water. Bring to a boil, reduce to simmer, and cook for 20–25 minutes until tender. Drain and let it cool slightly.
Prep the veggies: While the farro cooks, chop the cucumber, tomatoes, and red onion. Add them to a large bowl with chickpeas, olives, feta, and herbs.
Make the dressing: In a small bowl or jar, whisk together olive oil, lemon juice, Dijon, garlic, salt, and pepper until smooth.
Combine everything: Add the cooked farro to the bowl with veggies. Pour the dressing over and toss gently to coat.
Taste and adjust: Add a pinch of salt, extra lemon juice, or herbs to taste. Serve slightly warm or chilled.