- In a large bowl, combine cumin, coriander, paprika, turmeric, cinnamon, cayenne pepper, minced garlic, olive oil, lemon juice, salt, and pepper. Mix well to create a marinade. 
- Add the chicken thighs to the marinade, ensuring they are well coated. Cover and refrigerate for at least 1 hour, or overnight for best flavor. 
- Place the sliced onion at the bottom of the slow cooker. Add the marinated chicken thighs on top. Pour the chicken broth over the chicken. 
- Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the chicken is tender and easily shreds with a fork. 
- Once cooked, shred the chicken in the slow cooker using two forks, mixing it with the juices. 
- Serve the chicken in pita bread or flatbreads, topped with cucumbers, tomatoes, red onion, and a drizzle of tahini sauce.