Place bread cubes in a bowl and toss in oil or melted fat (that has been allowed to cool) with salt and seasoning (if using).
Spread bread cubes on a parchment-lined rimmed baking sheet, and place the sheet on the middle rack of a pre-heated 350°F oven.
After 7-8 minutes, open the oven and remove the baking sheet to a heat-proof surface.
Toss bread cubes using a spatula, and redistribute them evenly on the baking sheet.
Return bread cubes on the baking sheet into oven, and continue to bake for the remaining time for a total of 15 minutes.
Check bread cubes at 15 minutes. If they are a golden brown, remove them from the oven. If they are not quite a golden brown yet, allow them to bake for another minute or two until the desired color is obtained.
Allow croutons to cool before storing them in an airtight container in the pantry or the refrigerator. Croutons will stay fresh in the pantry or the refrigerator for approximately 2 weeks or up to 2-3 months in the freezer.