Place the bacon in a large skillet over medium heat. Fry until browned, then remove to paper towels to drain. Add the butter to the bacon grease. When the butter begins to sizzle, sprinkle 3 tablespoons of flour over it. Reduce the heat to medium-low, and cook for about 12 minutes, stirring frequently, until dark brown. Don't let it scorch - if it starts to, just reduce the heat.
When the roux reaches dark brown, increase the heat to medium-high, and add the onions and bell pepper. Cook and stir for a couple of minutes, just until softened. Meanwhile, place the shrimp in a bowl, and toss with seasoned salt, pepper, garlic powder, and remaining flour. Pour into the pan, and stir constantly for 1 minute. Whisk in the chicken stock, and reduce the heat to low. Cook for just a few minutes to thicken the broth. Don't cook much longer, or the shrimp will become tough. Sprinkle the chopped green onion over it, and remove from the heat. Serve over fresh hot grits, rice or biscuits. Crumble the bacon slices on top.