Real World Fly Fishing features a virtual fly tying desk where you can add your favorite fly patterns to the game, or create your own original flies. This feature is even used by a commerical fly tying company to design the flies that their tyers produce.
Simply select a hook and thread and then click to add components. Add tails, bodies, ribs, wings, hackles, even weight, beads and specialty components. You can resize and reposition any component and even change the color of any material. When you're done you can name your new fly and you'll find it in your flybox in the game.
The video to the right was created by a fan of the game, demonstrating the feature while creating a streamer.