In a medium bowl, combine the ground beef with the flour, chili powder, salt, minced onion, paprika, onion powder, and garlic powder. Use your hands to thoroughly mix the ingredients into the ground beef.
Add the beef mixture to the water in a skillet over medium heat. Mix well with a wooden spoon, and break up the meat as it cooks. Cook until browned. The finished product should be very smooth and kind of pasty, with no large chunks of beef left. In a separate bowl, combine sour cream and green onion ends.
Heat up the taco shells in a preheated 375 degrees F oven for about 5 minutes. Build each taco by spooning 2 tablespoons of the meat into a warm shell. Sprinkle some cheese over the top of the meat. Spread some of the sour cream over the cheese and then add shredded lettuce. Serve immediately.