Pick over lentils to remove any stones or debris. Put them in a large pot and wash them in several changes of cold water. Drain and set aside. (You can eliminate this step if the package says lentils are washed and presorted.)
Heat the corn oil in large skillet and saute onions, celery and garlic until vegetables become translucent. Transfer to crockpot. Add water or chicken stock, bouillon cubes, carrots, and lentils. Cover tightly and cook on low for 18-24 hours. Season to taste. Makes 8 to 10 servings. Freezes well.