Sear the pork roast in a hot skillet with olive oil for about 2 minutes per side to build a crust. Transfer to the slow cooker.
Whisk the reserved pineapple juice, soy sauce, brown sugar, minced garlic, grated ginger, and rice vinegar in a bowl.
Pour the liquid over the meat in the slow cooker. Scatter the pineapple chunks around the roast.
Cook on the low setting for 6 to 7 hours until the internal temperature reaches 145°F.
Rest the cooked meat on a cutting board under foil for 15 minutes before slicing.
Strain the cooking liquid into a saucepan and bring to a boil. Whisk in the cornstarch slurry and boil for 2 minutes until thickened into a glaze.
Serve the sliced pork over rice, drizzled generously with the thickened pineapple glaze.
