Wash the wall to prepare it for the mud relief sculpture. Sand the wall with a coarse-grit sandpaper to create a rough surface so that the mud sticks to the wall.
If making a free standing sculpture, choose a base for the piece. A concrete base works best.
Sketch the design for the sculpture and make a wire frame, also known as armature. The armature holds the sculpture together. If you plan to make a relief sculpture, draw the shape of your sculpture on the wall using chalk. Insert nails in the wall following the outline of the sculpture. Add a few nails inside the outlined area and tie wire around the nails.
Prepare the mud using fine clay soil, sand and water. Add equal parts of soil and sand and mix with water to obtain a homogenous paste. This way there won't be cracks in the sculpture once the mud dries.
Apply a thin layer of mud on the wall or the free-standing wire frame. Use a palette knife or your hands, while wearing rubber gloves. Allow the mud to dry.
Apply a thicker layer of mud and shape it according to the desired design. Allow the piece to dry.
Seal the sculpture using diluted PVA glue.
Paint the sculpture using water-based colors. Color the relief sculpture in the same color as the walls or choose a complementary color.