Trim excess fat from the pork shoulder and cut into 2-inch chunks.
Place the pork in a slow cooker and add the orange juice, lime juice, minced garlic, cumin, oregano, sea salt, and black pepper.
Cover and cook on low for 7-8 hours or on high for 4-5 hours until the meat is tender enough to shred with a fork.
Once cooked, 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. Add the shredded pork and a splash of the cooking liquid from the slow cooker.
Press the pork down with a spatula and cook for 3-5 minutes without stirring until the bottom is browned and crispy.
While the pork crisps, warm the corn tortillas in a separate dry pan or over an open flame until pliable.
Thinly slice the radishes and finely dice the red onion and cilantro.
Divide the crispy pork carnitas between the two tortillas.
Top with the sliced radishes, diced red onion, and fresh cilantro before serving.