Using the flat side of your knife, chop and mash salt and garlic together on a cutting board into a smooth paste. Transfer paste to a large bowl and stir in cumin, paprika, and turmeric.
Stir in 3 tbsp oil and then add chicken thighs and drumsticks. Toss until evenly coated. Cover bowl with plastic wrap, and marinate in the refrigerator for 4 hours.
Heat remaining oil in an 8 qt Dutch oven or large tagine over medium-high heat. Working in batches, add chicken pieces and cook, turning once, until golden brown on both sides, about 10 minutes. Transfer to a plate and set aside.
Add saffron and onions to pot. Season with salt and pepper and cook, stirring occasionally, until soft (about 15 minutes).
Return chicken to pot along with lemon slices and 1 cup water and bring to a boil. Reduce heat to medium-low, and cook, covered, until chicken is cooked through (about 40 minutes).
Remove from heat and scatter olives and cilantro over chicken. Serve over rice.