Rice paper can be stuck to a cake in a few simple steps. First, ensure that the surface where the rice paper will be placed is clean and dry. Next, lightly moisten the area with some water or by brushing a small amount of clear piping gel onto the surface - this helps in adhering the rice paper smoothly without wrinkles or air bubbles. Gently place the rice paper onto the moistened area and press down lightly with clean hands or a smoothing tool to ensure it sticks securely. Allow it some time to dry completely before adding any additional decorations around or on top of it. It's important not to use too much moisture as it might cause the rice paper to become overly soft or disintegrate.