Rinse the lentils under cold water and remove any debris. In a medium-sized pot, bring the water to a boil and add the lentils. Reduce the heat to low and simmer for about 20-25 minutes, or until the lentils are tender but still hold their shape. Drain and set aside to cool.
In a large bowl, combine the cooked lentils, red bell pepper, cucumber, red onion, kalamata olives, parsley, and mint. Toss to combine.
In a small bowl, whisk together the lemon juice, olive oil, salt, and pepper. Pour the dressing over the lentil mixture and toss well to coat. Adjust seasoning to taste.
In a separate bowl, lightly coat the feta cheese cubes with flour, shaking off any excess. Heat the vegetable oil in a skillet over medium-high heat. Fry the cheese cubes for about 2-3 minutes on each side, until golden brown and crispy. Remove from heat and drain on paper towels.
Add the fried cheese cubes to the lentil salad and gently toss. Serve immediately and enjoy!