The lentils cook all day in the slow cooker, but the ham and spinach are added at the end for optimal flavor and texture.
Rinse and drain lentils. In an electric crockery cooker combine lentils, water, onion, celery, carrot, bouillon granules, garlic, lemon peel, and red pepper.
Cover and cook on low-heat setting for 7 to 8 hours. (Or, cook on high-heat setting for 3-1/2 to 4 hours.) Add ham. Cook, covered, on high-heat setting for 10 minutes more. Stir in spinach; serve immediately. Makes 4 to 6 servings.