Preheat oven to 300 degrees.
Remove crusts from sourdough and discard (or save for homemade croutons!)
Cut sourdough slices into small cubes and divide among two baking sheets.
Bake for 5-7 minutes, remove from oven and stir/flip, then return to oven for another 5-7 minutes.
Remove the dried bread cubes from oven (leave the oven on for second baking) and, working in batches, pulse in a food processor for approximately 2 minutes per batch until course crumbs form. Be sure your crumbs are fairly uniform in size to prevent burning when using them to bread and bake fish, chicken, or vegetables.
If making seasoned crumbs, stir in the 21 Seasoning Salute
Return the pulsed crumbs to the baking sheets and spread evenly around the pan. Bake for 8-10 minutes or until lightly golden.
Remove from oven and allow to dry completely on the pan.
Store in an airtight container in the pantry or, to keep longer, in the freezer.