Rinse off the pork shoulder, and pat it dry with a paper towel.
In a small bowl, combine the oregano, cumin and olive oil into a thick paste.
Rub mixture all over the pork shoulder and place it in the slow cooker.
Add in the salt, pepper, garlic, and onion, and squeeze the orange juice over the top of all of it.
Turn the slow cooker on high and let it cook for 6 hours.
Remove the pork from the slow cooker and place it in a large bowl (it will be falling apart completely, so work carefully).
Use a fork and shred the pork.
Strain the leftover liquid from the crockpot (save for later)
Immediately before serving, fry the pork in small batches in a single tablespoon of oil, and a few tablespoons of the leftover liquid from the crockpot for two minutes. Remove from the pan and place it directly on the plate. **Don’t skip this step, as it is what gives the pork texture and that little bit of crisp that it needs.**
Serve on a fried flour or corn tortilla, or by itself.
Top with another couple of tablespoons of the juice from the crockpot. The juice is salty and will give it a richer flavor.