Preheat oven to 375°F and line a large baking sheet with parchment paper.
Cut off the top inch of the sourdough boule. Using a small serrated knife, slice around the inside leaving a 3/4-inch thick wall and bottom. Pull out the center bread portion in whole chunks and cut them (along with the top lid) into bite-sized cubes for dipping and set aside.
In a large mixing bowl, mix together the softened cream cheese and Hiland Rockin Ranch Dill Dip until smooth and uniform. Fold in the Monterey Jack, mozzarella, minced garlic, red pepper flakes, and 1/4 cup of the Parmesan cheese until evenly distributed.
Fold in the dry spinach and chopped artichokes until fully combined.
Spoon the filling tightly into the prepared sourdough bowl, pressing down slightly to fill any gaps. Top the dip with the remaining 1/4 cup of Parmesan cheese.
Place the filled bread bowl in the center of baking sheet and arrange the bread cubes around it. Stir the garlic powder into the melted butter and brush it generously over the exposed bread rim and the bread cubes. Bake for about 20-25 minutes until the dip is hot and bubbling around the edges, and the top Parmesan crust turns light golden. If the dipping cubes toast too quickly, pull them off the sheet with tongs halfway through.