Season the pork shoulder evenly with ground cumin, dried oregano, sea salt, and black pepper.
Place the seasoned pork in a slow cooker along with the orange juice, lime juice, and minced garlic cloves.
Cover and cook on low heat for 8 hours or until the meat is tender enough to shred easily with a fork.
Remove the pork from the slow cooker and shred into bite-sized pieces using two forks.
Heat olive oil in a large cast-iron skillet over medium-high heat.
Add the shredded pork to the skillet in a single layer and press down with a spatula, searing for 3-4 minutes until the edges are crispy and golden.
Warm the corn tortillas in a dry pan or over an open flame until pliable.
Assemble the tacos by dividing the crispy pork between the tortillas.
Top each taco with a dollop of Greek yogurt, diced white onion, and fresh cilantro before serving.