1. Pat pork shoulder with a paper towel to absorb liquid. Set aside.
2. Place a large cast iron skillet or other heavy pan on the stovetop over medium high heat. 
3. While the skillet is heating, prepare the pork rub. In a small bowl, combine the garlic powder, onion powder, rosemary, paprika, thyme, salt, and pepper. Mix well, then rub all over the pork. 
4. Add the oil to the hot skillet and swirl to coat. When the oil is hot, place the pork in the skillet and sear for about 2 minutes on each side.
5. Meanwhile, place the onion in the bottom of the slow cooker. When the pork is seared on all sides, place it over top of the onion in the slow cooker. 
6. Deglaze the skillet by adding the broth, wine, and minced garlic to the hot skillet. Scrape the bits off of the bottom of the pan and bring the liquid to a boil. Reduce the heat and simmer the liquid for 2 minutes to allow the flavors to combine. Stir in the mustard. Pour the liquid over the pork in the slow cooker. 
7. Top the pork with the potatoes and carrots. Sprinkle the potatoes and carrots with salt and pepper then add the fresh herb bundle.
8. Cover the slow cooker and cook on low for 6-8 hours. You’ll know it’s done with the pork falls apart easily and the vegetables are fork tender.

Optional step (to make the gravy): 

1. To make the gravy, transfer about 1 ½ cups of the liquid from the slow cooker to a small saucepan. 
2. In a small dish, stir together 1 tablespoon of water with 1 ½ tablespoons of cornstarch until a smooth slurry forms. Slowly add the slurry to the liquid in the saucepan. Bring to a boil over medium-high heat. Reduce the heat to maintain a simmer. Whisk continuously until thickened, about 2-3 minutes. 
3. Remove from heat and season with salt and pepper to taste. Serve gravy over the pork and vegetables.