Place the corned beef brisket in the slow cooker, fat side up. Add the spice packet, water, onion, and garlic.
Cover and cook on low for 8-10 hours or until the meat is tender.
Once the corned beef is cooked, remove it from the slow cooker and let it rest for 10-15 minutes.
Add the carrots and potatoes to the slow cooker and cook on high for 30 minutes until tender.
Preheat the oven to 400°F. Line a baking sheet with foil.
Slice the corned beef against the grain into ½-inch thick slices and place them on the baking sheet.
Drizzle the olive oil over the sliced corned beef and season with black pepper, paprika, garlic powder, and onion powder.
Bake in the preheated oven for 15-20 minutes, or until the edges are crispy.
Serve the crispy corned beef with the cooked carrots and potatoes. Garnish with fresh parsley.