We used card board egg container to form the rectanguler shape.
The technique of forming round shape balls the size of a cherry was used, they filled the egg container with round shape balls. Once the container was full they rubbed the shapes together to make it smooth and flat. I like this technique because I do not have to worry about kneading the clay well, and you get a very special boarder edge.
To make the design "a wave" , they worked on paper.
They cut the design and placed it on the clay, using a stick they traced the line.
It was colored with a mix of gauche and glue.
Shells were pressed in the clay to decorate while the glue/paint are still wet.
When dry add a layer of glue on entire art project.