In a small saucepan, bring 3/4 cup water and a pinch of sea salt to a boil Stir couscous into the boiling water, cover with a lid and remove from heat. Let sit for about 5 minutes or until all the water is absorbed. Set aside and allow to cool, then fluff with a fork. Cut the pre-cooked chicken into bite-size pieces. Place lettuce in the bottom of salad bowl. Layer on chicken, cucumber, tomatoes and red onion. Top with 1/2 cup cooled couscous. In a Mason jar with a lid, add dressing ingredients and shake until well-combined, about 15 seconds. Pour the vinaigrette over the salad. Add crumbled olives and feta and toss lightly. Serve at room temperature. Serve with toasted pita if desired.