Using a serrated knife, carefully cut a 1 to 1-1/2 thick horizontal slice from the top of the boule, to create a flat round top. Remove the middle of the loaf by pulling it out to create a bowl. Dice the bread into large cubes for dipping. Cook the bacon in a large skillet until crisp. Remove paper towel to drain, reserving 2 tablespoons of the bacon fat in the pan. Add onion and cook until translucent and softened slightly. Add the spinach and artichoke hearts, turning occasionally until the spinach is wilted. Stir in flour. Stir in the remaining ingredients except for the bacon, and heat until cheese is melted. Once the cheese is melted, pour mixture into a food processor and/or blender and pulse on low speed 2-3 times to break up the large pieces of spinach. Pour the mixture into the boule, top with crumbled bacon and serve accompanied by the bread cubes.