Rinse and pick over the lentils to remove any small rocks or stray grains. Place the lentils in a large bowl and cover with water. The water should be 2-3 inches above the lentils. Let sit overnight or at least 1 hour.
Preheat the oven to 325F. Drain the lentils and place them in a large dutch oven. Add the water, stock, garlic, bay leaves, and 1 teaspoon of salt to the dutch oven. Stir to combine. Place the lid on top and place in the oven for 45-60 minutes, until the lentils are cooked through.
Meanwhile, in a large bowl, combine the olive oil, vinegar, olives, shallots and 1 teaspoon black pepper.
When the lentils are done, remove and discard the bay leaves and garlic cloves. Drain the lentils and add them to the bowl with the olive oil mixture. Stir to combine. Adding the lentils to the dressing when they are still warm helps them to absorb the flavors.
I like to make a big batch of this salad and keep it in the refrigerator for lunches during the week. I would suggest adding the feta and mint just before serving. I just sprinkle a little feta and fresh mint over each portion before serving. If you are serving the whole lentil salad all at once, add the full amount of the feta and mint to the salad.
Serve the salad by itself, or over greens with sliced avocado and pepitas. Enjoy!