Cut a square out of your fabric. The bandanna size will depend on your cat’s neck and collar size. The collar I used is about 9 inches (not including the clasps), so I cut out a 9 by 9 inch square.
With the wrong side of the fabric facing you, turn two opposite corners 2½ inches, with the pointed end of the corner facing the center. Then press with your iron.
Fold the square with the right sides together, matching the two unfolded corners, and pin in place.
Starting just below a folded edge, sew one side of the bandanna using a ¼-inch seam. Repeat on the other side
Turn bandanna right side out, using one of the openings.
Use a pencil or chopstick to flatten out the side seams and the bottom, then press with your iron.
Now it’s time to make the pocket the collar will go through. Lay your cat’s collar over the top of the bandanna, where the openings are. Include the clasps, so you can make enough room for the whole collar to slide through. Use the water soluble pen to draw a line just under the collar — this will give you a guide to sew a straight line for the pocket. Sew across the marked line, then use a damp cloth to remove the mark.