To prepare the chicken shawarma marinade, combine the lemon juice, olive oil, garlic, paprika, cumin, pepper, salt, turmeric, and red pepper flakes to a small blender or bowl and mix until well combined.
Add the chicken thighs to a shallow bowl, tray or resealable freezer bag and pour in the marinade. Toss until the chicken is well coated. Store in refrigerator for at least 1 hour or up to 12 hours.
When ready to cook, preheat oven to 425 degrees. Brush a tablespoon of oil evenly across a rimmed baking sheet. Remove the chicken thighs from the marinade and place evenly spaced out on the greased pan.