Preheat oven to 350 degrees Fahrenheit.

Cut sourdough bread into 1-inch squares.

Place bread squares on a baking sheet.

Drizzle olive oil over the bread.

Toss the bread to coat with olive oil.

Sprinkle salt, pepper, and crushed red pepper flakes over the bread.

Add grated Parmesan cheese to the bread.

Toss again to combine all ingredients.

Bake in the preheated oven for 10-12 minutes, or until golden brown and crispy.

Let cool slightly before serving.