Purl Soho has a delightful tutorial on their blog — coasters of nautical signal flags! Using canvas and wool threads, you’ll fin detailed instructions on how to make them.
The charts for the flags are not included in the post, you’ll have to design your own. But that is very easy to do. Begin with a flag alphabet, below, (each flag represents a letter); find the one you want. Once you have your canvas cut or the coaster size marked, use an extra-fine marker safe for fabrics to mark the lines for the flag on the canvas.
You’ve made a great and useful project!