There are a few different ways that you can make a dog bed out of old pillows. One way is to fold an old pillow in half, and then sew the edges shut. You can also use a hot glue gun to attach the edges together.
Another way to make a pet bed out of an old pillow is to cut it into a square or rectangle, and then sew or hot glue the edges together.
If you want, you can also add some more stuffing to your pet bed before you sew or glue the edges shut.