Pat the chicken dry and sprinkle all over with salt and pepper.
Heat a 12-inch skillet over medium-high heat and add the olive oil.When the oil shimmers, add the leek, carrot, celery, thyme, and ¼ tsp salt and sauté until the vegetables soften, about 3 min­utes. Add the chicken and continue to cook until the bottom of the pan has turned a rich brown, about 4 minutes longer. Add the garlic, orange juice, and tomatoes with their juices and bring to a simmer, stirring to scrape up the browned bits from the bottom of the pan. Reduce the heat to low, cover, and simmer the stew until the chicken is tender and shreds easily, about 30 minutes. Using a slotted spoon or tongs, transfer the chicken thighs to a large plate and let cool slightly. When cool enough to handle, cut or shred the meat into bite-size pieces. Return the chicken to the pot and add the olives, half of the parsley, and half of the orange zest. Taste and season the stew with more salt and pepper to taste.
Serve over hot cooked rice, garnished with remaining parsley.