This recipe is my mom's specialty and she has handed this recipe and method down to each of her kids. It tastes like home to me and I make it for all the holidays in our house. I love how it fills my whole house with it's delicious aroma! Sometimes I open the door and walk outside for a minute just so I can come back in and smell it! I love the idea that one day I will be teaching my girls this recipe and they will be making it in their own homes.
For the pot roast and gravy: Bring the roast to room temperature, about 20 minutes.
Season the roast with the salt and pepper. Rub the entire roast with the garlic, tucking into the roast's nooks and crannies as you go.
Heat the oil in a large Dutch oven over medium-high heat. Brown the roast until golden brown all over, about 4 minutes on each side. Pour in the beef broth. Layer the onion and pepper slices on top of the roast and bring the liquid to a boil. Cover and reduce the heat to low. Cook until the meat is fork-tender, 4 to 5 hours. Discard the onions and peppers. Remove the cooked roast to a serving platter. Let cool, then shred with two forks.
Whisk the flour with 1/4 cup of warm water in a liquid measuring cup or small bowl until smooth. Heat the juices remaining in the pan over high heat until boiling. Slowly whisk in the flour mixture and cook over medium-high heat, whisking constantly, until thickened, about 5 minutes. Let cool slightly.
Add 1 cup of gravy to the shredded and cooled meat. Mix until it resembles pulled pork and all the meat is thinly coated with the gravy.
For the horseradish mayo: Combine the mayonnaise and horseradish in a small bowl and mix until combined.
For the sliders: Add an even layer of horseradish mayo on the bottom of the slider buns. Add a layer of the pot roast to the slider buns and then top with the dill pickles.
Reserve the remaining gravy and pot roast for another use.