Smoke it low and slow at 225–250°F for 10–14 hours until it hits 195–205°F internal and probes tender. Braise it in the oven at 300°F for 5–6 hours with aromatics and liquid. Slow cooker on low for 10–12 hours also works for braised brisket.
Brisket has two muscles, the flat (leaner, slices cleanly) and the point (fattier, great for burnt ends). Low and slow isn't optional. Rush it and you get tough, chewy brisket. Be patient.
Brisket comes from the chest of the animal, a very hardworking muscle. That's why it takes so long. All that connective tissue and fat needs time to break down. When it does, you get meat that's tender, rich, and deeply flavorful.
Keep frozen until ready to use for up to 12 months. Thaw in the refrigerator overnight, or quick thaw in a bowl of cold water if you're in a hurry (just keep it in the sealed package). Keep thawed brisket in the fridge for 1-2 days, or refreeze immediately if not using.