In a bowl, whisk together the reserved pineapple juice, soy sauce, brown sugar, minced garlic, minced ginger, salt, and pepper until the sugar is fully dissolved.

Place the pork shoulder chunks into the bottom of the slow cooker.

Pour the pineapple juice mixture evenly over the pork, making sure all pieces are coated.

Cover and cook on LOW for 6-8 hours or on HIGH for 3-4 hours, until the pork is very tender.

During the last hour of cooking, add the drained pineapple chunks to the slow cooker.

In a small bowl, mix 1 tablespoon cornstarch with 1 tablespoon cold water to form a smooth slurry.

Remove the pork and pineapple from the slow cooker and set aside. Pour the remaining cooking liquid into a saucepan over medium-high heat.

Add the cornstarch slurry to the saucepan and stir constantly until the sauce comes to a boil and thickens, about 2-3 minutes.

Return the pork and pineapple to the slow cooker and pour the thickened sauce over everything.

Garnish with chopped green onions and serve warm over jasmine rice, quinoa, or cauliflower rice.