If you will be doing hand appliqué, you might try Jeana Kimball’s backbasting needle turn method. This method allows you to turn the edge on just a small section at a time. With that large of an appliqué, after marking the design in reverse on the back, I would probably glue baste the appliqué on the front to the background to make sure everything lays flat, even if that means sometimes have to fight the glue when trying to turn the edge. Best of luck.