Cut the pork butt into 2-inch chunks. Trim fat and of course the bone if present. Mince jalapeno. Crush or mince garlic. Add the meat to a large mixing bowl and coat with the juice of a large orange and two limes. If cooking closer to 3 lbs. use only one lime and a smaller orange.
Add two teaspoons coarse salt, one teaspoon black pepper, one teaspoon cumin and one teaspoon oregano. Add garlic and jalapeno and mix well.
Prep a large crock pot with a good spray of Pam. Add the meat and cook on low for 5-6 hours and check the internal temperature. You are looking for 190 plus. Once there, remove enough liquid to leave about half the meat exposed. Save the juice for later. Cook for one more hour with the top open to vent the moisture.
Remove the Carnita's and cover with foil for 10-20 minutes before serving. Add the juice to the previously removed juice and refrigerate for reheating. Skim the fat after cooling.
Pork can be cooked in covered dish in oven, microwave or stove top after cut into chunks. The browning is important.