Make the Swag
Hang a curtain rod across the top of your window if one is not already in place. Make sure your rod extends several inches out from the window to give you room to wrap the swag around the back of the rod when you drape the fabric.
Decide how far down the sides of the window you want your swag to hang. This is a matter of personal preference. The swag could extend all the way down to the windowsill or even puddle on the floor. It also could drop as little as 1 foot from the top corners. Ending the swag shorter than a foot on the sides is not recommended, as the fabric will tend to stick out rather than hang nicely. Measure and record the side lengths.
Drape the tape measure around the curtain rod in the manner that you want your fabric to hang. For instance, if you want three loops of fabric across your curtain rod, wrap the tape measure three times around the rod and pull it to achieve the desired loop effect. Record this measurement from corner to corner. Add side lengths to this measurement to arrive at the length needed for your swag.
Cut a rectangle of fabric 24 inches wide and the length of your swag. Fold the fabric in half lengthwise with right sides together. Using a 1/2-inch seam, sew both short edges and all but 12 inches at the center of the long edge, which is left open for turning. Press the seams flat. Do not press the folded edge. Trim fabric at the corners to reduce bulkiness.
Pull the fabric through the opening to bring right sides of fabric to the outside. Use a pointed object, such as a knitting needle or sharpened pencil, to push out the corners, being careful to not poke a hole through the fabric.
Fold over the raw edges of the opening. Use thread and a hand sewing needle to make tiny stitches to sew it closed. Drape fabric over curtain rod as desired.
For each rosette, cut a 7 x 20-inch strip of fabric.
With wrong sides together, sew the short ends of the strip together to form a circle.
Fold the fabric in half lengthwise with wrong sides together, so that the right side of the fabric is facing out. Use a zigzag stitch on your sewing machine to finish raw edges and prevent unraveling.
With a hand sewing needle and a doubled length of thread, weave long running stitches around the zigzagged edge, 1/4-inch in from the edge. Pull the thread to gather the rosette, leaving a 3/4-inch wide opening at the center of the circle.
Hold the rosette up to the corner of the swag. Pull a puff of swag fabric through the opening. Move the rosette out of the way temporarily and wrap a rubber band around the puff to secure the fabric. Put the rosette over the puff of fabric and fluff out the fabric to hold the rosette in place and hide the rubber band and the inside edge of the rosette.