Special equipment: a small smoker box
Set a rack on a rimmed baking sheet. Rinse the brisket well, discarding the brine. Refrigerate, uncovered, overnight until the brisket has formed an outer crust. Remove the brisket from the fridge and allow it to come to room temperature, about 1 hour.
Combine the peppercorns, coriander and mustard seeds in a spice grinder and grind coarsely. Combine with the brown sugar and rub a thick coating into the top of the brisket.
Meanwhile, preheat the oven to 250 degrees F. Line a roasting pan with several long pieces of aluminum foil, leaving significant overhang on all sides.
Fill a small smoker box with wood chips and follow the manufacturer's instruction for lighting the chips. Once the box is billowing smoke, carefully put it in the center of the prepared pan using oven mitts or tongs. Place a roasting rack upside down over the smoker box so that there are a couple inches of clearance between the top of the smoker box and rack.
Place the brisket, fat-side up, on the rack and close up the foil, leaving plenty of air circulating around the brisket. Place the pan in the oven and smoke until the brisket reaches an internal temperature of 150 degrees F, about 4 hours. At this point, the brisket can be cooled down, wrapped well and refrigerated overnight or frozen for up to 3 months, until ready to steam and serve.
To steam: Preheat the oven to 300 degrees F. Set a roasting rack in a roasting pan. Pour 1 cup water in the pan and place the brisket, fat-side up, on the rack above the water. Cover tightly with foil and steam until the brisket reaches an internal temperature of 200 degrees F, about 3 hours. Let rest for 20 minutes, then slice thinly against the grain and serve with mustard on rye.
Combine the salt, sugar, juniper berries, peppercorns, cloves, thyme and bay leaves with 1 gallon water in a large stockpot. Bring to a boil over high heat and stir until the salt and sugar are dissolved, about 3 minutes. Remove from the heat and allow to cool completely, about an hour.
Pour the brine over the brisket, weighting the brisket down with a heavy plate to ensure it's completely submerged. Cover, and transfer to the refrigerator to brine for 1 week.
Remove the brisket from the brine and discard the brine. Rinse the brisket well in cold water.