How to Make It
Preheat oven to 475°F. Whisk together first 4 ingredients, 3 tablespoons of the oil, and 1 3⁄4 teaspoons of the salt in a large bowl. Add chicken, cauliflower, carrots, red onion, grapes, and lemon wedges; toss to coat. Spread mixture on a large rimmed baking sheet in a single layer. Place chicken pieces on top, skin side up. Roast in preheated oven until vegetables are tender and a thermometer inserted in center of chicken registers 165°F, 35 to 40 minutes.
Transfer vegetables and chicken to a platter; tent with aluminum foil. Scrape any juices and browned bits from baking sheet into a small saucepan over high. Whisk in lemon juice, cornstarch, and 1⁄4 cup of the stock. Bring to a boil, whisking constantly, until thickened, 2 minutes. Remove from heat; add butter and 2 tablespoons of the parsley. Whisk until butter melts.
Bring remaining 1 1⁄2 cups stock, 1 tablespoon oil, and 1⁄4 teaspoon salt to a boil in a medium saucepan over medium-high. Add couscous; stir and cover. Remove from heat; let stand 5 minutes. Fluff couscous with a fork. Divide couscous, chicken, and vegetables among 4 serving plates. Top with sauce, almonds, and remaining 2 tablespoons parsley.