Next fit your food processor with the shredding disc.
Cut all the crusts off each slice of bread. Cut the crustless bread into strips to make the bread easier to fit into the food chute.
Scatter breadcrumbs onto 1 or 2 rimmed sheet pans and bake for 20 to 30 minutes, tossing every 5 minutes or so until crisp. Panko crumbs should not be golden.
Allow the crumbs to cool completely before storing in an air-tight container for a few weeks or freeze for up to 2 months or so.