In a gallon size freezer bag, mix the flour, chili powder, salt, garlic powder, ground cumin, and black pepper.
Add the carne asada beef, seal the bag, and toss to coat the meat.
Place a 10 to 12 inch skillet over medium high heat. Add the oil. When the oil is hot, add the beef mixture and press down.
When the bottom is brown, flip the beef to brown on the other side.
Transfer the beef to the slow cooker.
With the skillet still over the heat, add the water and scrape the bottom of the skillet with a wooden spoon to remove any stuck on pieces.
Pour this liquid over the meat in the slow cooker.
Mix together the tomatoes and green chiles. Pour over the meat.
Cover and cook the beef on high for 3 hours or low for 6 hours.
Serve with a slotted spoon. Use the carne picada for tacos, tostados, or nachos. Top with avocado, sour cream, chopped cilantro, sliced radishes, or shredded cheese.