Prepare Dressing: In a mixing bowl, combine fresh lemon juice, minced garlic, salt, black pepper, and optional chili flakes. Whisk together until well blended, then gradually drizzle in olive oil while whisking to emulsify. Set aside.

Cook Lentils: Rinse lentils under cold water. In a medium pot, add lentils, water, and bay leaf. Bring to a boil, then simmer uncovered for 20-25 minutes until tender. Drain and remove bay leaf.

Combine Ingredients: While warm, transfer lentils to a large bowl. Pour dressing over lentils and toss gently. Let sit for 10 minutes to absorb dressing.

Add Vegetables: Chop cucumber, bell peppers, green onions, parsley, and mint into bite-sized pieces. Add to lentils and toss gently.

Adjust Seasoning: Taste the salad and adjust seasoning as needed with salt, pepper, or lemon juice.

Serve or Chill: Serve salad at room temperature or refrigerate for up to three days. Allow it to come to room temperature before serving.