In a food processor or a blender combine garlic, salt, smashed peppercorns, orange and lemon juice, onions and oregano. Process until smooth.
Heat 1/2 cup of olive oil in a saucepan, the oil should be hot but not deep frying temperature hot.
Take it off the heat and stir in the contents of the food processor and keep stirring to avoid burning.
Pour the mixture of the pork and let it marinate overnight.
In the morning put the pork together with the marinade in a slow cook and cook on low for 8 hours.
At the end of cooking time pull pork with two forks and mix it well with the juices.