It's easy to work in groups of 9 squares as the units are 3x3. You can cut as many squares as you like out of muslin or any other fabric to make the windows themselves. We chose 8-1/2" prewashed and pressed unbleached muslin.

Go to the sewing machine. Fold each square in half and stitch a 1/4" seam from the folded to the raw edge.

Continue sewing the folded squares one after the other in a chain to save a little time and thread.

When you have completed the stack of squares, snip the length of folded and stitched squares into individual pieces again, turn them over, and stitch closed the opposite side. Again, stitch from the fold to the raw edge and use a chain type of sewing.

Trim the corners of the completed rectangles. (The photo does not show trimmed corners.) Fold the seamed edge of the resultant rectangle to meet the opposite seamed edge, right sides together. Place a pin at the junction of the seamlines.

Stitch the folded upon itself rectangle, leaving an approximately 1" opening for turning.

Taking care not to stretch and distort the fabric, turn the square inside out (seams inside), shaping and sharpening the corners. Press the square. Do not iron - press only. Please note that the "straight" edges are now on the bias of the fabric.

Slip stitch the opening used for turning closed. (This will not show on the finished product.)

As shown in the picture, turn one corner to the center and press.

Continue to turn the corners in and press. You can pin the corners down at this point and tack the center later or move on in the project.

For our project, we're going to add a button to the back of each square.

To tack the four corners down and to stitch the button on, take care to catch the corners on one side while putting thread through the holes of the button on the other side of the square. The goal is to secure the button and tack down the four corners. The tacking of the corners will show on the finished product, so do this with a truly complementary thread and tidy stitching.

As mentioned above, we're going to work in groups of 3, so complete three units/squares as noted.

Button sides together, pin squares and slip stitch them one to the other. This stitching will not show in the finished product.

Sew three rows of 3 squares together as above (button sides together, pin, and slip stitch). Again, the stitching will not show on the finished project.

Pin an approximately 2" square of fabric to each window on the non-button side of the growing "quilt".

Turn down the edges of the "windows". This is a bias piece of fabric and will curve naturally as shown. I usually pin down each piece to hold it in place while I work. The pinning does not provide an exact window frame for you, but it does provide a guide as you blind stitch/hem stitch the frame to the colorful fabric window.

Continue to pin the frames of the windows to the window fabric.

NOTE: Nine squares of fabric prepared as above create 12 panes for windows.

Following the blue line in the photo, hem stitch or blind stitch the frame to the window fabric. Try NOT to go through all layers of fabric; the windows should "float". This isn't a hard and fast rule; you may want the windows to not float if you're using the fabric for a vest or other garment. The traditional Cathedral Window, though, has stitching going through the window and the window frame only.