Step 1: Pick windows, measure and cut.
Step 2: Design a Face.
Step 3: Cut out the pieces.
Step 4: Pop the Face in Place
Remember when you do this, that viewers outside will see the reverse image, like a mirror!
Step 5: Night / Day
Inspect during the day too. If the brown cardboard or colored poster that you used looks a little 'off' with the colors of your house, then you can paint it a matching color!