Corrective grow-with-me sandal: If the deformity is caught early on, when the chick is still growing, trace around the chick's foot on a piece of paper using a pencil.
Using coffee stirrers, pipe cleaners, wooden skewers or other similar material, cut to the length of the chick's foot, as if it were it's normal appearance.
Secure the pipe cleaners (or similar-like material) to the toes of the chick using Vetwrap or duck tape (even normal tape would work). It should be snug but not too tight, as you don't want to cut off circulation in the chick's foot.
Secure the cardboard (or similar-like material to the bottom of the chick's foot and to the pipe cleaners.