Preheat the oven to 400ºF. Cut the bread into 1/2-inch cubes. You should have about 4 loosely packed cups of bread cubes.
Place the cubed bread in a large bowl and drizzle the olive oil over top. Use a spatula or your hands to gently toss the bread cubes until they are coated in oil.
Combine the Italian seasoning blend, garlic powder, and salt in a small bowl, then sprinkle the mixture over the bread cubes. Gently toss the bread cubes again until they are evenly coated in seasoning.
Spread the seasoned bread out onto a baking sheet. Transfer the baking sheet to the oven and bake for about 10 minutes*, checking the color of the bread every 5 minutes. Stir the croutons and bake for an additional 2-3 minutes, if needed, to get the croutons to a nice deep golden brown color. Let the croutons cool slightly before serving.
*The cook time can vary significantly depending on the density and moisture level of the bread (whether it is stale or fresh), so check the croutons every five minutes.