In a mixing bowl, combine the reserved pineapple juice, soy sauce, brown sugar, minced garlic, minced ginger, salt, and pepper. Whisk until the sugar dissolves.

Cut the pork shoulder or pork butt into 1–2 inch cubes for even cooking. Place in the slow cooker.

Pour the prepared sauce mixture over the cubed pork, ensuring it is fully coated. Stir gently.

Cover the slow cooker and cook on low for 6 to 8 hours or high for 3 to 4 hours.

During the last hour of cooking, gently fold in the pineapple chunks.

Mix cornstarch with 2 tablespoons of water to create a slurry, stirring until smooth.

After cooking time, remove pork and pineapple using a slotted spoon. Reserve the cooking liquid.

Transfer the reserved cooking liquid to a saucepan and bring to a simmer. Whisk in the cornstarch slurry until thickened.

Return the pork and pineapple to the slow cooker, pour the thickened sauce over, and stir gently.

Sprinkle chopped green onions over the dish before serving.