In Mexico, Frijoles de la Olla (slow cooked beans in a pot) are typically prepared in large clay pots over an open fire with pepper and spices. You can achieve similar results at home with a large pot or a pressure cooker!
Soak the beans in a pot of water overnight. Drain.
Heat the olive oil in the pot over medium heat. Add the onion, garlic, jalapeno and cumin and cook, stirring occasionally, about 5 minutes. Add the oregano and the beans, then add enough water to cover (about 9 cups). Increase the heat to medium high and bring to a boil, then reduce the heat to medium low, partially cover and cook, stirring occasionally, until the beans are just tender, about 3 hours.
Add 2 teaspoons salt and simmer, uncovered, stirring occasionally, until the liquid is mostly absorbed, about 45 minutes. Season with salt. Let sit 15 minutes before serving; top with queso fresco and cilantro, if desired.