In a large wide pan or flameproof clay casserole, heat 3 tablespoons of the olive oil over medium heat. Add the leeks and cook, stirring, for about 8 minutes to soften. Stir in the garlic. Add the lentils and stir to coat with the oil. Pour in enough water to cover the lentils by 2 inches (5 cm). Add the bay leaves and oregano sprigs, raise the heat slightly, and bring to a boil. Cover, reduce the heat to low, and simmer for about 30 minutes, until the lentils are al dente but not completely cooked. The lentils will have absorbed almost all the water by the time they are ready to come off the stove. Discard the oregano sprigs and bay leaves.

Preheat the oven to 375ºF (190ºC).

If you were using a metal pan, empty the lentils into a clay or glass baking dish with a lid. Toss the lentils with the remaining olive oil, the coriander, cumin, honey, vinegar, and salt to taste. Add enough water or vegetable broth to cover the lentils by about ½ inch (1.5 cm). Cover and bake for 45 minutes to 1 hour, until the lentils are tender but still retain their shape. Check on the liquid content during baking and add additional water or broth as needed. The end result should not be soupy or too wet, but rather the lentils should have absorbed all the liquid in the pan, expanded nicely, and not disintegrated or dried out.