Heat the sauce in a small pot until just starting to boil. Whisk in the arrowroot powder until smooth. Remove from heat.
Portion the teriyaki sauce over the chicken thighs, reserving about ¼ cup.
Cook for 30 minutes before pouring the remaining sauce overtop of the chicken and baking for 10 more minutes or until chicken thighs reach 170 degrees Fahrenheit on a meat thermometer.
Broil for 2-3 minutes watching closely.
Remove from the oven, let them sit for 5 minutes and then serve.
Video
Notes
If you want more sauce to pour on top after they're cooked or to make bowls with, whisk together another half batch of the gluten-free teriyaki sauce and combine 1tsp of arrowroot powder. Heat at a rolling boil until sticky.
Pouring the ¼ cup of sauce on top of the thighs after they bake for half an hour keeps the tops juicy.
Try not to have your chicken thighs directly against each other, or they won't be coated as well in the sauce.