First, a large block of foam must be procured. If you're in the SF Bay Area, check out Bob's Foam Factory; tell him Nicodemus sent you! (You probably won't get a discount, but you might make him chuckle.)

If there are no specialty foam outlets in the area, try an upholstery shop. Blocks of foam can be attached, surface-to-surface, using a foam-friendly adhesive such as 3M Super77 or Fastbond 100. From this initial block, the head structure is carved; ears are often carved separately and attached to the head later.

Sketching appropriate profiles on the foam with a marker helps greatly during the carving process. Additionally, as the head begins to take shape, use a pair of cardboard eyes (as seen above) on the carving; this adds "life" to the character.

Carve a hollow cylindrical area for the wearer's head. This is usually towards the "back" of the head, reserving more space to carve the muzzle. Keep cutting away until the cavity is sized so that it fits snugly over the head of the wearer. Once the exterior of the head is finished, you can carve out additional space to make breathing easier and possibly install a fan to improve ventilation. Some people prefer to have a sturdier head mount. Carve the head space to be a bit larger and glue a (cheap) bike helmet into the hollow; this also provides a chin strap for extra security. If you want a simpler harness, try buying a cheap hardhat and removing the plastic headband and rigging.

Once the hole is made for the wearer's head, begin carving the outside into a rough representation of the shape of the character's head. On the first pass, simply remove large chunks, without trying too much for a final shape or profile. Be sure to monitor the symmetry of the carving. Progressively carve the shape down until it is the right size and character. The best thing for cutting through stiff foams is an electric carving knife; X-Acto Knives work well for "digging" through the foam.

A lot of time will be spent making sure the various ridges of the head are correctly proportioned and symmetrical. Do not worry about small details on the surface; the fur will hide and smooth these imperfections. In fact, it is often helpful to drape small pieces of fur across the head to see how the features will look with the added "bulk" of the fur. Avoid making the foam too thin at any point. General rule is to keep at least a half-inch thickness in all major surfaces.

Once the carving is finished, apply fur to the sculpture. This will require numerous small pieces in order to properly match the curves of the foam head; by paying vareful attention to edges and nap, however, it is fairly easy to hide seams.