Begin by cutting up your stale sourdough bread into small cubes. Place in a large bowl.
Drizzle olive oil over bread cubes and mix well - making sure every piece is coated in oil. You do not want it soaked - only lightly coated.
Sprinke in Italian seaoning and mix until distributed evently on all pieces.
At this point you may choose to add a little more oil or seasoning to your taste. You just want to make sure you do not saturate your bread in oil.
Spread pieces in a single layer on a cookie sheet.
Bake for 20 minutes. Take the sheet out of the oven and flip the pieces over as best you can.
Return to eh oven for another 20 minutes.
Remove from the oven and stir one more time. Then let the croutons cool completely - about 3 hours - before moving to an air tight container.
Notes
If you are using sourdough that has inclusions like cheese or fruit, you may need to increase the time you bake. You want them to be totally dried out but not overcooked.