Seals have been used for hundreds of years to show that documents were genuine. In ancient times, they carried the emblem of the owner, usually with a ring of text or a banner around the outside identifying the owner (or sometimes carrying their motto.) The practice of sealing documents with a personal or family symbol dates back to Ancient Rome, and its believed that the tradition of family heraldry came from the practice of handing down a seal from generation to generation.
Leave some room at the edges of the design. Seals work better if the edge of the matrix is smooth.

When you have your design finished, you must flip your art horizontally. The process of leaving an impression in the wax will flip it back.