Season the pork shoulder with sea salt, black pepper, cumin, and dried oregano, rubbing the spices deeply into the meat.
Place the seasoned pork in a slow cooker along with the minced garlic, orange juice, and lime juice.
Cover and cook on low for 8 to 10 hours until the pork is tender enough to fall apart with a fork.
Remove the pork from the slow cooker and shred it using two forks, discarding any large pieces of excess fat.
Heat a large non-stick skillet over medium-high heat and add the shredded pork in a single layer.
Press down with a spatula and sear for 3-4 minutes until the bottom is golden and crispy.
Warm the corn tortilla in a separate dry pan until pliable and slightly toasted.
Fill the tortilla with the crispy pork and top with diced red onion, fresh cilantro, and thin slices of radish.