Some vintage patterns are available on various websites, but I decided to forgo the purchased patterns and find a tutorial on the internet.
This website by essortment was where I went for general instructions. Of course, the pattern was tweaked and re-sized, but the general gist of it was used. I found that after washing my fabric, it did shrink up, so be sure you prewash your yardage, and purchase enough to allow for shrinkage. And ensure that if you are taller than average that you increase your length.
Weekend Designer highlighted this caftan, along with similar technique instructions.