Defrost banana leaves.
Cook the bacon in a heavy skillet until crispy. Remove bacon slices, leaving rendered fat in the pan.
Sprinkle the pork with salt and pepper, then brown pork in the bacon fat until browned on all sides. Place pork into a crockpot.
Add chopped onion, bell pepper, and tomato to the same skillet, along with the garlic salt, cumin, 1 packet Goya seasoning, and chile powder, and sauté over medium heat until tender and fragrant, about 5 minutes. Add vegetables to crockpot with pork.
Add vinegar, brown sugar, and beef stock (or wine).
Turn crockpot on to low, and cook for 8 hours, or until meat is very tender and easy to shred.
Using 2 forks, roughly shred meat while still inside crockpot and let cook for 1 more hour.
Strain meat, reserving juices. Place strained meat and vegetables in a bowl and set aside. Reserve 1 cup of the juices for the dough, and place the rest in a saucepan. Simmer until thick, then stir into shredded meat. Filling can be made ahead and refrigerated for up to two days.
Make dough: Add masarepa or masa harina to a large bowl. Gradually stir in the 1 cup of reserved crockpot juices. Stir in 3 cups of chicken stock and a packet of Goya seasoning.
Slowly add a little more chicken stock, stirring, stopping when cornmeal comes together into a soft dough. Work in the lard with your fingers. You should have a soft, piable dough.
Rinse the banana leaves and gently dry them. Banana leaves are huge, so I cut them into rough rectangles for the tamales. Experiment with the size you prefer (large, appetizer-size, etc).
For a medium tamale, cut the leaves into rectangles about 8 x 10 inches. Lay the rectangle down flat, and place about 1/2 cup of dough in the middle. Press the dough into a rectangle about 2 1/2 by 4 inches. Place a couple of tablespoons of filling on top, and sprinkle with raisins, nuts, and olives if desired. Top filling with another 1/2 cup of dough, and press into rectangle.
Wrap filling with leaf: fold in right side, then left, then turn up the bottom, then turn down the top. Secure tamale with string.
Repeat with remaining filling and dough.
Place several tamales (as many that will fit easily) into a steamer basket insert, and place basket over a pot of boiling water, keeping tamales above the water. (see How to make humitas ). Cover tamales with a kitchen towel, then with a pot lid, and steam for 30-45 minutes, being careful to replenish the water in the pot when necessary.
Let tamales cool, then serve. Steamed tamales can be frozen. Reheat them by steaming them or simply microwaving them.