This paper proposes a method to design protective foam for packaging 3D objects. Users first load a 3D object and define a block-based design space by setting the block resolution and the size of each block. The system then constructs a block map in the space using depth textures of the input object, separates the map into two regions, and outputs the regions as foams. The proposed method is fast and stable, allowing the user to interactively make protective foams. The generated foam is a height field in each direction, so the foams can easily be fabricated using various materials, such as LEGO blocks, sponge with slits, glass, and wood. This paper shows some examples of fabrication results to demonstrate the robustness of our system. In addition, we conducted a user study and confirmed that our system is effective for manually designing protective foams envisioned by users.