Being very careful not to cut all the way through the pork roast, slice roast down the center, cutting about ¾ of the way through. Unfold the roast so it lays open. Then, repeating the previous step, slice ¾ of the way through each of the halves so that the meat lays flat. There should now be three cuts in the meat. Set aside.
Combine Herb Rub 1 ingredients in a medium bowl. Mix until combined.
Rub herb mixture on inside portion of roast. Tie roast back together and set aside.
Combine Herb Rub 2 ingredients in a small bowl. Mix together until combined.
Distribute Herb Rub 2 over the outside of the pork roast.
Place steam rack into Instant Pot. Add vegetable stock.
Place prepared roast onto steam rack. Pressure cook on high for 90 minutes.
Allow steam to release naturally. Remove lid. Check to make sure roast is tender and easily shredded. If needed, pressure cook the roast on high for an additional 15 minutes. When finished, allow steam to release naturally.
Add root vegetables to Instant Pot. Set pressure to low and cook for 3 minutes. Allow pressure to release naturally.
Remove vegetables and pork roast. Slice or shred roast and serve with the freshly cooked root vegetables and drippings.
If desired, make a pork gravy (recipe found in Country Pork Ribs recipe). Serve with mashed potatoes, if desired.