In a medium bowl or large measuring cup, whisk together the store-bought teriyaki sauce, chicken broth, honey, minced garlic, and grated ginger until the honey is dissolved and everything is evenly combined.
Pour the teriyaki mixture evenly over the chicken thighs in the slow cooker, making sure all of the chicken is coated in the liquid. Use a spoon to nudge the thighs so some sauce gets underneath as well.
Cover the slow cooker with the lid and cook on LOW for 4 to 5 hours, or on HIGH for 2 to 3 hours, until the chicken is very tender and easily pulls apart with a fork.
Once cooked, taste the sauce and adjust if needed by adding a splash more teriyaki for extra saltiness or a drizzle of honey for more sweetness. If you prefer a slightly thicker sauce, transfer 1/2 cup of the cooking liquid to a small saucepan and simmer on the stovetop for 3 to 5 minutes to reduce slightly, then pour it back over the chicken.
Gently shred or roughly chop the chicken thighs directly in the slow cooker using two forks, stirring to coat the pieces evenly in the teriyaki sauce.
