Place the chuck roast on a large plate. In a small bowl, mix 1 tablespoon salt, onion powder, garlic powder, and black pepper. Pat the chuck roast dry with a paper towel and coat it with the seasoning. Set it aside.

In the slow cooker, combine beef broth, french onion soup mix, sliced onions, minced garlic, thyme, worcestershire sauce, liquid smoke, and dijon mustard. Set aside 1/4 cup of this mixture next to the stove.

Heat a large cast iron skillet over medium-high heat. Add 2 tablespoons of butter until melted. Sear the chuck roast on all sides, then move it to the slow cooker.

Pour the reserved 1/4 cup of beef broth into the hot skillet. Scrape up any bits stuck to the pan. Add the remaining 2 tablespoons of butter and let it melt. Once the pan is clean, pour this liquid over the chuck roast in the slow cooker.

Cover the slow cooker and cook on HIGH for 4 hours or LOW for 8 hours. Once done, shred the beef using two forks.

Butter the inside of each hoagie roll. Add a good amount of onions and shredded beef, then top with cheese. You can also add horseradish mayo if you like.

Serve each sandwich with a small bowl of broth (or au jus) from the slow cooker for dipping.