Trim excess fat from the pork shoulder and cut into 2-inch chunks.
In a slow cooker, combine the pork chunks, sea salt, black pepper, dried oregano, ground cumin, orange juice, and lime juice.
Cover and cook on low for 7-8 hours or on high for 4-5 hours until the meat is fork-tender.
Remove the pork from the slow cooker and shred it using two forks, discarding any large pieces of fat.
Heat a 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 crispy and golden brown.
Warm the corn tortillas in a dry pan or over an open flame until pliable and slightly charred.
Divide the crispy pork between the two tortillas.
Top with pickled red onions, thinly sliced radishes, and fresh cilantro before serving.