Start by trimming excess fat from the chicken thighs and cutting them into large chunks, about 3-4 pieces per thigh. Place them in a bowl and set aside.
In a small bowl, whisk together soy sauce, honey, grated ginger, minced garlic, rice vinegar, and sesame oil until well combined. This will be your flavorful teriyaki sauce.
Pour the sauce over the chicken pieces, making sure they are coated evenly. Use a spatula to spread the sauce if needed, then transfer everything into your slow cooker.
Cover the slow cooker and cook on low for 4 to 5 hours, or on high for 2 to 3 hours. The chicken should become very tender and easy to shred with a fork.
Once cooked, remove the chicken pieces and set aside. Turn the slow cooker to high and uncover to allow the sauce to simmer and thicken for about 20-30 minutes, stirring occasionally. The sauce will become glossy and sticky.
If you prefer shredded chicken, gently shred the pieces with two forks and return to the thickened sauce, stirring to coat evenly. For a neater presentation, serve the chicken whole.
Serve the chicken over steamed rice, spooning the thick, glossy sauce generously over the top. Garnish with sliced green onions for a fresh burst of flavor and color.