In a large stock pot, combine all of the ingredients for the brine except the ice. Bring to a boil and stir until all of the salt and sugar has dissolved in the brine. Remove from the heat and stir in the ice until the brine has cooled to room temperature.
Place the brisket in a large food-safe plastic container and pour over the cooled brine. Keep the brisket in the cure in the refrigerator for 5-7 days, turning and stirring the brine mixture at least once per day.
Once the brisket is cured, you can prepare as corned beef. Recipe linked in the recipe notes. Or, if you like, you can follow the remaining instructions to make home cured pastrami.
In a small saute pan over medium heat, combine the coriander seed, mustard seed, and peppercorns. Toast the spices for 2-3 minutes or until just fragrant. Transfer to a mortar and pestle or a spice grinder and pulse until well combined. Stir in the remaining rub ingredients.
Coat the cured brisket in the pastrami rub and wrap tightly. For best results, let the roast sit in the pastrami rub for 1-2 days. Preheat your smoker and cook at 250 degrees until the internal temperature reads 195 degrees. This typically takes anywhere from 6-8 hours. Wrap the smoked pastrami in plastic wrap and chill completely before slicing thin and stacking high on your favorite rye bread.