Bring a large saucepan of salted water to a boil. Add the farro to the boiling water and cook until tender, about 20 minutes. (If cooking whole-grain farro it will take 30 minutes.) Drain well.
Add the olive oil and red pepper flakes to a large serving bowl. Add the tomatoes, mint, parsley, radishes, cucumbers and lemon juice and stir to combine with the oil. Toss in the farro while still slightly warm and combine with the salad. Top with the feta and season the salad with salt and pepper.