Season the chicken thighs with kosher salt and pepper on both sides and place them in the bottom of your crockpot.
In a medium bowl, combine the bourbon, brown sugar, soy sauce, and minced garlic. Stir well to mix.
Pour the sauce over the chicken in the crockpot, making sure the chicken is well-coated.
Cover and cook on low for 4 hours or high for 3 hours.
About 30 minutes before the chicken is done, mix the cornstarch with cold water in a small bowl to create a slurry. Whisk the slurry into the sauce in the crockpot to thicken it.
Once done, serve the bourbon chicken over rice and garnish with green onions if desired.