Using a craft knife, carve the clay into a rectangular piece roughly the circumference of the glass bottle and bend it gently around the bottle. (Tip: Clay will stick to glass if pressed against the surface, so use a light hand in working with clay on the bottle mold.) Add strips of clay to form the bottom portion of the vase, using your finger to smooth the joints. Add another strip to create a top lip. Use your finger to gently smooth the surface, join the creases, and use a small amount water to wet the clay along the seams. Use dampened sponge to smooth uneven surfaces.