Add the bottom linen panel: Cut linen to the width of the sheer plus 2 inches, and the height from the windowsill to the floor plus 4 inches. Fold 1/2 inch along top edge; iron. Pin the folded edge to the sheer, centering the linen panel to leave 1 inch on each side; stitch in place. Fold side edges in 1/2 inch, then 1/2 inch again; iron, and stitch in place. Fold bottom edge up 1/2 inch, then 3 inches; iron, pin, and stitch in place.