To thicken the stew use either the flour or the potatoes.
3tbspoil + 3 tbsp all purpose flour
Soak the beans in cold water overnight (12hours). Use a large bowl for that, the more water, the better. Rinse them well and pour them into a large pot. Add 3L (12.5 cups) of water and bring to a boil. Cook for about 20 minutes. Discard the water and add 2,5 L of boiling vegetable stock water. Cook at high heat for another 50 minutes.
Clean and cut the vegetables into even little cubes, not larger than the beans.
Saute the vegetables with the spices, salt and pepper in a large pan with 3 tbsp of oil for about 10 minutes. They should be softened and lightly coloured, not browned. Stir in the tomato puree until everything is evenly covered.
Add the vegetables to the beans and simmer over medium heat for another 20 minutes.
To thicken the stew you can either use flour or cooked potatoes. Option 1: If you are avoiding gluten then blend 4 cooked potatoes in a little bit of the vegetable stock that you take from the stew. Add the mix back to the stew and stir well. Option 2: For the more traditional route then Add the flour and oil to a saucepan. Stir well on low heat until slightly golden. Add a little bit of liquid from the stew at a time and keep stirring until you got a smooth and thick sauce. Pour it into the stew and give it a gentle stir. Cook on low heat for another 10 minutes or until it reached the desired thickness. The longer you wait, the thicker it will get,
I would not advise using canned beans since they will fall apart too much.