Place all pork carnitas ingredients in a slow cooker and cook on low for 8-10 hours.
Move an oven rack up to about 4-5 inches below the broiler heating element.
Prepare a rimmed baking sheet by lining it with foil and preheat the broiler.
Shred the pork, using a fork if needed, and use tongs to remove the meat to the baking sheet.
Spread the shredded pork into a single layer on the baking sheet. Taste the meat and add salt if needed.
Broil about 4-5 inches from the heat for 4-5 minutes or until a crust forms. To make the meat even crisper, remove the tray from the oven, turn the meat over, and broil the second side for an additional 4-5 minutes.
Serve with warmed tortillas, chopped red onion, and fresh cilantro leaves. Top with additional lime juice if desired.