Combine thyme, oregano, dill, salt, black pepper, garlic powder, and onion soup mix in a bowl. Season the pork on all sides. Press the seasoning into the pork.
Set the instant pot to sauté. Add olive oil to coat the bottom of the pot. Sear the pork for 4 minutes, flip, and sear the other side for 4 minutes. Searing will seal in moisture and flavor while giving the meat a delicious crust and color. In a pinch, you may skip this step, although we strongly recommend taking the extra time to do this.
Remove pork and set aside. Add a splash of olive oil, then add the onion, shallot, and garlic. Sauté for 2 minutes
Deglaze the pan with chicken stock. Scrape the bottom of the instant pot to be sure nothing sticks and burns.
Place the pork back in the instant pot atop the onions. Pour in the pickle juice and butter.
Seal and set to manual high pressure for 45 minutes. Allow natural release for 5 minutes, then quick release any remaining steam.
Remove pork and slice it.
Add carrots, celery, and potatoes to the instant pot and place pork on top. Add ½ cup stock and set to manual high pressure for 5 minute.