Step 1Fry the bacon in a large skillet over medium heat until crisp, 6 to 8 minutes. Drain the bacon on paper towels; pour off the drippings and reserve.
Step 2Cook the okra in half of the reserved drippings over medium-high heat, stirring constantly, about 10 minutes. Place the okra in a pot with the bacon and set aside.
Step 3Add the remaining drippings to the skillet and cook the onions and celery until the onions are tender, but not browned, 10 minutes. Add the garlic, mix well, then add half the tomatoes. Cook, stirring occasionally, until the tomatoes darken in color somewhat, 2 to 3 minutes. Add the remaining half of the tomatoes and simmer 5 minutes.
Step 4Pour the tomato mixture into the pot with the okra and bacon. Add 1 cup of boiling water and mix well. Add a second cup of boiling water and 1 bouillon cube. Stir over medium heat until the gumbo comes to a boil. Add a third cup of boiling water and the remaining bouillon cube and cook 10 minutes.
Step 5Blend the flour with the cold water until smooth. Add it to the boiling gumbo and bring the gumbo back to a boil, stirring constantly. Season it to taste with salt and pepper. Add the shrimp and simmer 5 minutes.
Step 6Let the gumbo stand 20 minutes before serving or refrigerate it overnight and reheat.