To make the croutons, cut the bread into 3/4-inch cubes. Heat a large skillet over high heat and add the olive oil, swirling to coat the bottom of the pan. Add the garlic and cook until it sizzles, about 50 seconds. Add the bread and cook, stirring, until golden brown, about 2 minutes. Discard the garlic. Sprinkle the croutons with the salt and serve over the lentil vegetable soup.