Place the roast on a large cutting board, fat cap side up. Trim the layer of fat to about ¼" thick. You don't want to remove all of it because it keeps the roast from drying out. Pat dry with paper towels.
Season with salt, then optionally slather Dijon mustard on all sides of the pork before applying the dry rub so it sticks better to the pork.
Rub the entire roast with the seasonings, pressing down to cover every inch thoroughly.
Place in a pan (stainless steel works best) and let it marinate for about an hour (or up to 24 hours) in the refrigerator, tightly covered. There's no need to bring it to room temperature before smoking because the smoking process is slow enough to cook it evenly, and cold pork absorbs the smoke better.
Load the hopper with wood pellets and preheat the pellet grill to 250-275℉ (120-135℃).
Place the roast directly on the pellet grill grates, fat side up, and put the pan underneath to catch the drippings (or leave it in the pan).
At around 4-6 hours, when the internal temperature reaches around 150-160℉ (65-70℃), you can wrap it in aluminum foil or butcher paper for moister pork. At this point, you can also add more dry rub and hot sauce if desired.
Put the wrapped roast back into the pellet grill and continue smoking until it reaches an internal temperature of around 205°F (95℃) and the pork shreds easily with a fork. It may take another 6-8 hours.
Remove it from the smoker and let it rest at room temperature for 30-45 minutes (make sure the internal temperature doesn't go below 140°F (60℃). You could also wrap it and let it rest 1-4 hours in a clean, dry insulated cooler.
Using kitchen gloves and shredding it with your hands is easiest, but you can also do it with a couple of forks.