Rub the pork with salt, pepper, garlic powder and onion powder.
Heat olive oil in a large skillet and sear the pork on all sides until browned (about 3-4 minutes per side).
While the pork is searing, add the onion, garlic, potatoes and carrots to the bottom of the slow cooker.
In a small bowl, whisk together the broth, vinegar, soy sauce, Dijon mustard, herbs (if using) and 1 ½ tsp salt.
Pour over the vegetables, stir thoroughly to coat them, then place the pork roast on top.
Add ¼ cup of water to the pork searing pan and scrape up any browned bits. Pour this into the crockpot, too.
Cover and cook on LOW for 9-10 hours or HIGH for 6-7 hours.
Transfer the cooked pork and vegetables to a plate and cover with foil to keep warm.
Spoon as much fat as you can from the remaining slow cooker liquid.
In a small bowl, whisk 3 tbsp cornstarch with 3 tbsp cold water until smooth.
Pour the slurry into the liquid in the slow cooker. Stir well to combine.
Cover the slow cooker and cook on HIGH for 10-15 minutes, stirring occasionally, until the liquid thickens into gravy.
Serve the pork with the vegetables and drizzle the gravy over the top.
