Preheat oven to 250°F (120°C)
Slice bread into cubes or tear into small pieces
Spread pieces in a single layer on a baking sheet
Bake 10–20 minutes, stirring every 5 minutes, until dry and lightly golden
Cool completely
Pulse in a food processor until desired crumb size
For coarse crumbs, pulse briefly
For fine crumbs, pulse longer
Spread crumbs back on the baking sheet if they feel soft, and bake 3–5 minutes more
Cool completely
Store in an airtight container
Freeze up to 3 months if needed