Get your campfire going and prep it so there is eventually a nice bed of hot coals to place your dutch oven on.
Place dutch oven hot coals, making sure it is stable and level. You may have to shift some of the coals around, or add a rock under the dutch oven to get it just right.
Heat 2 tablespoons of oil, and add the hash browns. Cook the hash browns until golden brown, stirring occasionally. You may need to add another tablespoon or two of oil if they start to stick. Season with salt and pepper.
Top hash browns with cheddar, spinach and sliced tomatoes, place the lid on the dutch oven, and heat until the cheese is melted. Remove from heat and serve with sliced avocado.