Heat the oil in a large pot. Add the cumin seeds, let them sputter a bit, then add the onions and carrots. Cook, stirring frequently over medium heat for about 5 minutes until the onions are softening.
Add the chopped tomato, sugar, black pepper, oregano and bay leaf. Continue cooking and stirring for several minutes until the tomatoes soften.
Sprinkle in the flour and quickly stir to cover all vegetables; then add the balsamic vinegar and soy sauce. Mix well.
Add the remaining vegetables, i.e. potatoes and green beans (or whatever else you like) and add the red lentils, mix well and then add the vegetable broth.
Cover, turn the heat low and simmer until all vegetables are cooked and you get a nice, thick stew. Keep an eye on it, stirring frequently; you may need to add more water.