Preheat oven to 450 degrees. Using a sharp knife, score the fat (but not the meat) on 1 boneless pork shoulder (7 pounds) in a diamond pattern. Season with coarse salt and ground pepper. Place pork, fat side up, in a roasting pan or large Dutch oven with 1/2 cup water. Roast until some fat has rendered, about 45 minutes. Remove pan from oven and reduce oven temperature to 350 degrees. Tightly cover pan with foil or a lid. Cook until meat is very tender, about 4 hours. When cool enough to handle, remove fat from top of roast. Using two forks, shred meat into bite-size pieces, discarding any large pieces of fat.
Refrigerate shredded meat in airtight containers, up to 3 days. If desired, reserve fat and render by cooking over low heat until mostly liquid. Strain and refrigerate; use in place of oil.