Put the garlic, black pepper, oregano and olive oil in a small food processor and chop it all up to bits. (If you don’t have a food processor that will deal with the small amount, just mince the garlic and combine everything together.)
Rinse the pork shoulder and pat dry. Remove the large layer of fat that sits on the top of the shoulder. There is plenty of fat marbled within the meat so you really don’t need this ½ inch thick layer.
Take a paring knife and stab some holes throughout the pork. I usually make an X and then shove my finger in there to widen the hole.
Shove the garlic mixture into these holes. Don’t worry if some ends upon the outside of the pork. It is not a big deal
Sprinkle the adobo seasoning over the pork and put it into your crockpot.
Cook on low for 6-8 hours or high for 3-5 or until pork is tender.
Remove the pork from the crockpot and either cut up and serve or cut up and put it back in the crockpot to sit in the juices for a bit. (this is my preferred option
I've had some people tell me that they take the pork out and shove it in the oven to get the crispy bits that really make pernil. I haven't tried this myself but I think it's worth a shot.
Recipe by Pirate Jeni at http://www.piratejeni.com/2011/05/31/crockpot-pernil/