Cut any of the large visible chunks of fat off the chicken (optional) and put the thighs in the bottom of the slow cooker. Sprinkle on the zaatar seasoning and rub all over the chicken to coat it thoroughly.
Place the goat cheese into a medium, microwave-safe bowl and microwave until the goat cheese just begins to soften, about 15-30 seconds. Add all the rest of the ingredients (except the full lemon and mint) into the bowl and whisk until smooth and the cheese is broken down.
Pour over the chicken, making sure to cover it. Place the 2 lemon halves into the slow cooker.
Cover and cook on low heat for 4-5 hours, until the chicken is cooked and tender. OR, high heat for 1-2 hours (low is recommended.)
Once cooked, squeeze out all the juice from the lemons into the slow cooker. Transfer the chicken to plates and then stir together the remaining sauce in the slow cooker until well mixed.
Spoon the sauce over the chicken and garnish with mint, if desired.