Preheat the oven to 325° F. Cut the boule in half. Pull 1-inch pieces from the inside. Toss the croutons in a bowl with the extra-virgin olive oil and salt. Spread the croutons in a single layer on a rimmed baking sheet and bake until golden brown and crisp, 10 to 12 minutes. The croutons should be lightly colored and crisp throughout.