What is the best way to: How do I make the mold for casting my coaster ?

Possible answers: --Use an old laminate shelf, cut a 12" by 12" square from it and four 1" by 12" strips that will be glued to the sides of the square with super glue.. --Use an old laminate shelf, cut a 12" by 12" square from it and three 1" by 12" strips that will be glued to the sides of the square with super glue..
Answer:
Use an old laminate shelf, cut a 12" by 12" square from it and four 1" by 12" strips that will be glued to the sides of the square with super glue.