Slicing Flank Steak
Whether you're cutting flank steak when it's raw or after it's been cooked, the best way to do it is across the grain.
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"Across the grain" means to cut across the fibers of the meat, rather than with them. Cutting across the fibers makes them shorter so the meat is easier to chew. For most flank steaks, this means slicing across the width of the steak rather than its length.