Materials: brown and orange paint, black cardstock, scissors, craft glue, hot glue, green pipe cleaner, magnet
Begin by painting the shell brown. Let it dry. Use your finger to rub orange paint over the shell. The goal is to cover most of the brown, letting some of the brown from between the ridges show through. While that is drying, use micro-tip scissors to cut facial features from black cardstock or construction paper. Anything goes. Glue them to the front with craft glue. Fold a 1" piece of green pipe cleaner in half and glue it to the back with hot glue, letting just enough stick up to look like a stem. Attach a magnet to the back with hot glue.
That's all there is to it!