Position the oven rack in the center and preheat to 300°F (149°C).
Place the cubed bread into a food processor. Blend at high speed for about 30 seconds to create coarse crumbs, or continue processing for up to 1 minute for a finer texture.
Evenly distribute the crumbs on a large baking sheet or divide them between two smaller pans, ensuring they lay in a single layer.
Bake for 5 minutes, then stir the crumbs to promote even drying. Return to the oven for another 5 minutes, checking for a light golden color and a dry texture.
If additional drying is needed, bake for another 2 to 5 minutes until completely crisp.
Allow the breadcrumbs to cool directly on the baking sheet for 10 to 15 minutes.
Store in an airtight container once fully cooled. If a finer consistency is desired, pulse the dried crumbs in the food processor until the preferred texture is achieved.