In a medium bowl, whisk together the pineapple juice, soy sauce, brown sugar, ketchup, grated ginger, and minced garlic until smooth.
Place the chicken thighs in the slow cooker in an even layer.
Pour the sauce mixture over the chicken, cover, and cook on low for 5–7 hours (about 420 minutes) until the chicken is tender and cooked through.
Remove the chicken from the slow cooker and set aside on a plate.
In a small bowl, whisk the cornstarch with 2–3 tablespoons of the cooking liquid until smooth, then stir this slurry back into the slow cooker to thicken the sauce; simmer on high for 5–10 minutes if needed.
EITHER serve the thighs whole with the sauce spooned over them, OR shred the chicken with two forks and return the shredded meat to the sauce, stirring to combine.
Serve warm on rice, in sandwiches, or as desired.
