Preparation of Ingredients: Start by placing the pineapple chunks, along with the juice contained in the can, into the slow cooker. This process allows the pork to marinate and tenderize as it cooks.
Seasoning and Searing the Pork: In a separate bowl, combine the chili powder, onion powder, salt, and pepper. Thoroughly rub this spice mixture over the entirety of the pork loin to coat it well. Preheat a large skillet with the oil over medium-high heat. Once the oil is hot, sear the pork loin for approximately 2-3 minutes per side or until a golden crust forms on each side.
Cooking: Carefully transfer the seared pork loin to the slow cooker, setting it on top of the pineapple chunks. Cover the slow cooker and set it to cook on low heat. The cooking duration should be between 4-6 hours if you prefer the pork to be sliced or up to 8 hours if you desire the pork to be easily shreddable.
Thickening the Sauce: This step is optional and can be employed if a thicker sauce is desired. Once the pork is thoroughly cooked and tender, remove it from the slow cooker. In a small bowl, blend the arrowroot flour with water to create a smooth slurry. Pour this mixture into the slow cooker and stir well to incorporate it into the juices, allowing the sauce to thicken effectively.
Final Preparation: After thickening the sauce, either slice or shred the pork loin, according to preference. You may then return the pork to the slow cooker to mix with the sauce and pineapple, or alternatively, plate the pork and generously drizzle with the sauce. Serve while hot.