Place the pork in a large Dutch oven or heavy pot. Add the orange juice, lime juice, garlic, cumin, salt, and enough water to just barely cover the meat. Most of the meat should be covered, but it's okay if the tips stick out - they will still cook in the steam. Bring the pot to a boil and then reduce the heat to a simmer. Simmer uncovered for two hours. Don’t touch the meat.

After two hours, increase the heat to medium-high. Occasionally stirring and turning the pieces of meat, continue to cook for about 45 minutes, or until all of the liquid has evaporated, leaving only the rendered pork fat. Let the meat sizzle in this fat until it browns at the edges, turning pieces gently (to prevent them from falling apart) to brown the other side.

When pork has browned on both sides, it’s done. Add seasonings to taste, if necessary. Serve on warmed tortillas with a scoop of slaw and desired fixings.