Combine olive oil, lemon juice, garlic, and spices in a large bowl.
Add chicken thighs and toss until evenly coated.
Cover and marinate for at least 2 hours.
Heat a skillet or grill pan over medium-high heat.
Cook chicken for 5–6 minutes per side until fully cooked.
Remove chicken from pan and let rest for 5 minutes.
Slice chicken into thin strips.
In a bowl, whisk together all garlic sauce ingredients until smooth.
Warm flatbread or pita.
Assemble shawarma with chicken, vegetables, and garlic sauce.
Serve immediately while hot.