Preheat the oven to 275 degrees F.
Layer the vegetables and the meat into the Dutch oven in this order: potatoes, beef, onions, bell pepper.
Using a small bowl, stir the curry paste into part of the coconut milk to dissolve it. Add more coconut milk and stir. Pour over the meat and vegetables. Use a little more coconut milk to get the last of the curry paste out of the bowl. Pour the second can of coconut milk evenly over the other ingredients. Sprinkle the fish sauce over everything, and sprinkle with salt.
Cover the Dutch oven with foil and seal as tightly as you can. Place the lid of the Dutch oven on top of that.
Place in the oven and roast for 6 or 7 hours.
After roasting, stir the curry and test for salt and spiciness. You can add a little curry paste dissolved in water if you want it spicier. Stir in most of the minced cilantro.
Serve as-is or over rice. Garnish with additional sprigs or leaves of cilantro.