Or have them create a map based on another story. For instance, Goldie Locks And The Three Bears. Fill a classroom wall with maps based on stories. This book has many true facts about slugs. The snail is a bossy sort of person.
Every animal has a way of protecting itself.
Have the students research ways in which other animals protect themselves. Make puppets from old socks or glue faces on popsicle sticks. The students can make up dialogue for Sam and the snail. Have the students act this out in front of the class. They can include the second slug and the toad.