In a large bowl, mix together the chicken ingredients and refrigerate until ready to use. In a medium bowl, mix together the Tzatziki sauce ingredients and refrigerate until ready to use. In a medium bowl, mix together the cucumber salad ingredients and refrigerate until ready to use.
To assemble: Cut the pita or flatbread into wedges and place on a serving tray. Top each with a spinach leaf, then a spoonful of chicken, then the cucumber salad, tzatziki sauce and sprinkle with feta cheese.
Serve and enjoy.
Tip: The sauce, salad and chicken can all be made a couple days in advance and then assembled just before serving.