Cut the onion in half and place it in the bottom of a slow cooker.
Place the pork roast on top of the onion, fat side up.
Pour in the vegetable stock or water.
Cut the orange in half and squeeze the juice over top of the pork, then repeat with the lime. You can add the spent halves to the slow cooker, or discard them.
Add the garlic and jalapeno to the top of the pork, then sprinkle on the salt, pepper, cumin, and oregano. Lay the two bay leaves on top, as well.
Cover and cook on low for 8 hours.
Once meat is done, remove the oranges and limes and discard. You can either remove the onion and jalapeno or shred it and mix it into the pork.
Shred the pork with two forks. Remove it from the slow cooker with a slotted spoon and place on a baking sheet. Reserve the liquid in the slow cooker.
Place the baking sheet under the broiler, watching closely, until the pork is lightly browned and the ends start getting crispy, about 5 minutes.
Remove from the oven, toss with 1/4 to 1/2 cup of the juices from the slow cooker,
and serve, as desired.