Prepare the Bread Bowl:

1. Cut the Top Off: Using a sharp knife, slice off the top of the sourdough loaf to create a lid.
2. Hollow Out the Bread: Scoop out the inside of the bread, leaving a 1-inch thick shell. Reserve the bread chunks for dipping.
3. Brush with Olive Oil: Lightly brush the inside of the bread bowl and the bread lid with olive oil.

Prepare the Spinach Dip:

4. Mix the Cheeses and Cream: In a large bowl, combine the cream cheese, sour cream, and mayonnaise. Mix until smooth.
5. Add Seasonings and Spinach: Stir in the mozzarella, Parmesan, garlic, onion powder, salt, pepper, and red pepper flakes (if using). Fold in the spinach until evenly combined.

Assemble and Bake:

6. Fill the Bread Bowl: Spoon the spinach dip mixture into the hollowed-out bread bowl, spreading it evenly.
7. Wrap and Bake: Place the filled bread bowl on a baking sheet. Cover the bread bowl loosely with foil to prevent over-browning and bake in a preheated oven at 375°F (190°C) for 20 minutes.
8. Uncover and Finish: Remove the foil and bake for an additional 5-7 minutes, or until the dip is bubbly and the bread edges are golden.

Serve:

9. Arrange the Dippers: Place the reserved bread chunks, crackers, and vegetables around the baked bread bowl on a serving platter.
10. Serve Warm: Slice the bread lid into strips for dipping, and enjoy the gooey spinach dip straight from the bread bowl.