Start by drawing out a template of your ear, make sure to make it slightly wider so that you can curve it like a real cat ear. The measurements for my ear were 3.5" x 3.5" x 4.5".
Cut out your template. I wrote an F to mark the front.
Draw around the template on to felt using chalk.
Draw out four more ears, remembering to flip the template over before your draw your last two ears.
Cut out the felt ears and pin the corresponding fronts and backs of the ears together.
Cut a length of wire (if you're using my measurements, cut it at 12"). Bend the wire, in the middle, at a 90" angle. Lay it on top of the ear and bend the two tails, so that they match the curves of the ear.
Fold the wire tails, at the corners of the ear, inwards at a 90" angle so that they meet along the bottom of the ear. Wrap the two tails around each other, so that the shape is secure.
Make two of these, one for each ear and put to the side for the moment.
Take your ears and stitch around the two shorter sides, leaving the bottom side open. You can use a needle and thread for this but I used a sewing machine to save time.
Now you can place the wire frames inside the ears.
Fill the ear with stuffing so that it's nice and squishy.
Use a needle and thread to stitch up the the final edges of the ears.
Take two jewellery clasps and stitch the ears securely on to the clasps.
Clip the ears in to your hair and then bend the ears in to a desired shape.