Pre-heat the oven to 300ºF.
Remove the thick cut of fat on the meat down to ⅛” thick. If using pork shoulder from the bone, remove the meat from the bone. Then cut pork shoulder into large 2” cubes.
3.5 pounds pork shoulder, boneless
Add all ingredients into a large dutch oven (6.5 QT or larger).
2 oranges, juiced, 2 limes, juiced, 2.5 cups water, 1 tablespoon oregano, 1 teaspoon chili powder, 1 teaspoon cumin, 1 teaspoon garlic salt, 1 tablespoon garlic
Place the dutch oven with lid on, in preheated oven. Let braise until meat falls apart when prodded with a fork, about 2.5 hours.
Remove the pot from the oven.
Using a slotted spoon, remove the carnitas from the dutch oven and liquid and onto an unlined baking sheet.
Place pot on stove at medium high heat. Boil mixture until the sauce thickens and reduced in half, about 25-30 minutes.
While the liquid reduces, use two forks to pull apart the meat from the cubed pork into slim pieces. Spread the shredded pork carnitas over the whole sheet pan. Remove any large pieces of fat that didn't cook down.
After the liquid finishes reducing, pour about 1 cup of the liquid over the shredded carnitas and spread evenly.
Turn on the broiler and place the sheet pan on the middle-rack of the oven. Broil for 3-5 minutes, until meat is browned and edges are crispy. Remove from oven, flip the pieces of meat to the other side, and then broil again for 3-5 minutes.
Serve immediately over rice, in corn tortillas, or in buns.