In a large slow cooker, add onions, celery, carrots, potatoes, corn, lentils, garlic powder, oregano, thyme, soy sauce, bay leaves, peppercorns and vegetable broth. No need to stir. Cover and cook on Low for 8-10 hours or on High for 4-5 hours (with this soup longer is better). Discard bay leaves and peppercorns. Using an immersion blender, pulse a few times until desired texture - I like creamy with chunks. Garnish with herbs and Parmesan cheese/plain yogurt/tortillas chips and serve hot.