Rub the pork shoulder with ground cumin, dried oregano, sea salt, and black pepper.
Place the pork in a slow cooker with minced garlic, orange juice, and half of the lime juice.
Cook on low for 6-8 hours or until the meat is tender and shreds easily with a fork.
Remove the pork and shred it, discarding any excess large pieces of fat.
Heat a non-stick skillet over medium-high heat and add the shredded pork, pressing down to create a golden, crispy crust.
In a small bowl, whisk the Greek yogurt with the remaining lime juice to create the crema.
Warm the corn tortillas in a dry pan until soft and pliable.
Assemble the tacos by layering the crispy pork onto the tortillas, topped with diced red onion, fresh cilantro, and a dollop of lime-yogurt crema.