Put a piece of aluminum foil (about 1 square foot) on your countertop and shape into a concave curve. Place a piece of plastic wrap on top of the foil. Using a tablespoon, scoop one spoonful of the melted chocolate onto the plastic wrap and spread into the shape of a rainbow using the back of the spoon. Repeat with the remaining chocolate. Let the chocolate petals set for 10 minutes.
Gently peel the chocolate off of the plastic wrap and place on a tray lined with parchment paper until ready to use.