Rustic Slow Cooker Chicken

chicken thighs ((skin-on, bone or boneless))

small yellow onions ((halved and sliced about 1/4-inch thick))

garlic cloves ((thinly sliced or minced))

ginger root ((about 1 1/2 inches, peeled and thinly sliced or minced))

sea or kosher salt ((plus more to taste))

ground black pepper

water

Olive or vegetable oil

butter ((unsalted))

Fresh herbs for garnish ((optional but highly recommended))