Cut a 1-inch slice off the top of the bread loaf and set aside. With a paring knife, gently remove the bread on the inside of the loaf to form a bowl, leaving a 1-inch-thick bread shell along the sides and bottom. Cube the top slice and the center of the loaf to make croutons.
Fry the pancetta in an ovenproof skillet until golden brown and crisp. Drain on paper towels. Add the croutons to the skillet and coat them with the pancetta fat. Season with salt and pepper, then transfer the skillet to the oven and cook for 5 minutes. Place the bread bowl in the oven along with the croutons to make it crisp.
In a large bowl, combine the cheeses and flour. Season with pepper.
In a saucepan, heat the beer and garlic. Gradually add the cheese mixture, stirring until the cheese melts. Stir in the spinach and sambal.
Fill the bread bowl with spinach dip and place on a baking sheet. Bake for 15 minutes.