Spread the croutons evenly on a half sheet pan or cookie sheet and bake in middle rack of the oven for about 35 to 45 minutes depending on the density of the bread (until they're golden brown and don't yield to gentle but firm pressure - you can always cool one and try it to see if it's crunchy all the way through). Midway through, give the croutons a flip with a spatula, scooping up as many will fit on the spatula surface and flipping them like you would a burger.