Season both sides of the chicken with salt and pepper.
Heat a large skillet over medium-high heat, then add the vegetable oil and swirl to coat the surface of the skillet. Add the chicken, skin side down, and sauté until golden brown (about 5-6 minutes). Flip the chicken and cook 2 minutes more. Transfer the chicken to the slow cooker.
In a medium bowl, whisk together the hoisin sauce, soy sauce, honey, water, ginger, and garlic. Pour the sauce over the chicken in the slow cooker.
Cover and cook the chicken on high for 3-4 hours, or low on low for 5-6 hours. Flip the chicken half-way through to make sure all of the chicken infuses with the sauce.
To serve, spoon the chicken over a bed of rice, drizzle the sauce from the slow cooker over top, then garnish with sesame seeds and cilantro (if desired).
*While bone-in, skin-on thighs provide the best flavor for this dish, you can use boneless and skinless thighs or breasts. If using skinless meat, you can skip the sautéing step and add the meat straight to the slow cooker. Keep in mind that white meat can dry out faster than dark meat and the cooking time may need to be reduced accordingly.