Rub the pork shoulder chunks thoroughly with ground cumin, dried oregano, garlic powder, sea salt, and black pepper.
Place the seasoned pork into a slow cooker and pour the orange juice over the top.
Cover and cook on low for 8 hours until the meat is tender and easily pulls apart with a fork.
Remove the pork from the slow cooker and shred it using two forks, discarding any excess fat.
Heat the avocado oil in a large cast-iron skillet over medium-high heat.
Add the shredded pork to the skillet in a single layer and sear for 3-5 minutes without stirring until the bottom is crispy and golden-brown.
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 diced white onion, chopped cilantro, and thinly sliced radishes.
Finish with a dollop of Greek yogurt and a squeeze of fresh lime juice before serving.