1. In a small bowl, whisk together the honey, soy sauce, minced garlic, rice vinegar, sesame oil, grated ginger, and red pepper flakes (if using).

2. Place the chicken thighs in the slow cooker in a single layer, skin-side up.

3. Pour the honey garlic sauce over the chicken thighs, making sure to coat them evenly.

4. Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the chicken is cooked through and tender.

5. Once the chicken is cooked, remove it from the slow cooker and place it on a serving platter.

6. In a small bowl, mix together the cornstarch and water to make a slurry. Pour the slurry into the sauce in the slow cooker and stir to combine. Cover and cook on high for an additional 15-20 minutes, or until the sauce has thickened.

7. Pour the thickened sauce over the chicken thighs. Garnish with sesame seeds and chopped green onions, if desired.

8. Serve the slow cooker honey garlic chicken thighs hot with your favorite side dishes, such as rice or roasted vegetables.

Enjoy your delicious and flavorful slow cooker honey garlic chicken thighs!