Choose your topiary form according to the shape of your boxwood bush. If your bush is tall and narrow, pick something like a standing rabbit or a kangaroo. Elephants and bears work well for short, squat shrubs. Make sure to get a template and not a form to be stuffed with moss, though you can use the latter as a visual reference.
Gently pull the form apart (most of them split in half) and drive one half into the ground on either side of the bush. Make sure they are lined up so your animal does not end up lopsided.
Begin trimming around the edges of the template to remove excess foliage. Cut branches just above a leaf node, or small bump, to encourage swift growth so you can continue trimming later. Make the edges as complete as you can.
Trim away branches sticking out beyond the inside of the template. Many are curved to help you form the body more completely; trim the branches so they sit just inside the wire frame.
Wait about two to three weeks for new growth to form so you can continue creating your animal. You may leave the template in place during growth or store it to avoid rust and weather damage.