Start by placing the green grapes in the bottom on the glass. This makes up the bottom on the flag.
Next comes the yogurt. You could also use whipped cream or even cool whip for a dessert. The regular style of yogurt does tend to drip down between the grapes. If this bothers you, use a Greek style yogurt which is thicker.
After draining the mandarin oranges, add them to the top of the yogurt.