Hi You want to measure the bolster width and length. add at least 1 inch to the width to allow 1/2 inch for the long seam. Add 6 inches to the length. You have to have some extra to gather and some for the casing. You are basically making a tube. sew the drawstring casing first onto the ends. allow 2 1/4 inches for the casing. Folded over first 1/4 inch, press, then fold over 2 inches. Sew close to the edge to make the casing. You can make the drawstrings from the same fabric by folding it over 1/4 inch two times and sewing. After you have sewn the casings,  Sew the long seam first to make the tube. Inside the tube open up the casing seam and pull your drawstrings through the casing with a large safty pin to guide in inside the casing...put your bolster inside and gather up the drawstrings..Presto...Answer back if you have other questions...Donna