Return the beans to the cleaned pot and add enough water to cover them. Simmer for about 1 hour or until tender. Don't add salt as soon as you start cooking the beans because they will become tough. Rinse the beans again, drain well and put into a clay pot or baking dish.
Preheat oven to 200C. In a separate saucepan, pan put half of the olive oil, add the onion and cook until tender. Add tomatoes, celery, parsley, chili flakes, carrots, garlic, hot water, petimezi and cook the sauce for 20 minutes to let the flavors to combine. Season to taste.
Pour the sauce over the beans in the baking pan, so that they are well coated, and drizzle with the rest of the olive oil. You can also cover the beans with some slices to tomato at this point, but it is an optional touch. Cook for the beans for about 40-45 minutes, or until the sauce has thickened. Serve warm garnished with parsley, a sprinkling of dried rigani and crumbled feta.