I could not access your link. Here is a site that has many country type curtains that you can at least have a visual to refer to.
Light Airy Curtains | The Country Village Shoppe
After posting I saw where a few people found what you are wanting to make. I agree that they are just a longer version on a valance with the addition of a bias casing to the back to cause it to be able to draw up the curtain with strings. My all-time favorites I made were priscillas that criss -crossed. I loved those curtains in the country living room. Ah that was many years ago. LOL!