When kid, I used to make my own pirate maps painting a paper with brown shoe polish and burning the edges, but they always ended turn apart, so I make my cousin a durable one made of a piece of khaki fabric I found.
Step 1: Your design
First, draw the map on paper, i traced Costa Rica from a real map to include it. I came with the idea of make the islands look like an ouroboros, the dragon that bites his tail. And after ending the map, trace it on the fabric.