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.
Step 2: Paint the land
Shade a little the land with an old pilot so it won't stand out a lot and delineate it with a green pilot.
Step 3: Details
Then draw some sea creatures, ships and a wind rose.
Step 4: Shoe polish
Now paint the map with the shoe polish. After that, I splashed it a little with some brown ink I had to make it look dirtier.
Step 5: Burn it
Carefully burn the edges of the map and maybe some holes to make it more real.
Step 6: Last touch
To make it cooler, put tubes on the sides of the map.
I glued a brochette stick to the map so the tube won't come off.
Step 7: Finished
Decorate the tubes and put a string to tie up the map.