Create your armature. While some sculptors don't use armatures to make OOAK babies, they help your sculpture keep its shape when you bake the polymer-clay figure. For one baby, you'll need aluminum foil and a thick piece of wire about 2.5-inches long for the armature. Roll two egg-shaped balls of aluminum foil, one about half the size of the other. The smaller foil ball is for the baby's head, the larger is for the torso. Do not attach the two pieces of armature together yet.
Sculpt the baby's head. Use a picture of a baby as a guide: babies' faces are fuller than adult faces, and are very expressive. Take a piece of polymer clay, and flatten it to just under one-quarter-inch thickness. Wrap the clay around the foil armature for the head, and smooth the seams until you have a smooth, rounded head. Take a thin rod from your clay sculpting tools and create a dent in the front portion of your baby's head, just over halfway up the face. This will be the "eye line," where you create the eye and brow areas on your baby. The top ridge will indicate the brow area, so the eyes will be placed in the indentations you've made.
Sculpt the eyes and nose. Create a small, three-dimensional, triangular shape to represent the baby's nose. Place this in the center of the eye line that you pressed into the head earlier. Don't smooth it out yet, as you're just placing the pieces for now. Roll two small egg shapes of the same size to represent the baby's eyes. Press these two pieces gently on either side of the nose. Now that you have the pieces placed to represent the eyes and nose, you can use your sculpting tools to smooth out the edges. Your baby's eyes will be closed. Smooth the edges to create the bridge of the nose and the nostrils. Remember, a baby's nose is more bulbous at the tip and more turned up, so you'll be able to see the nostrils a bit more than you would on an adult head.
Smooth the edges around the eyes to blend into the brow you created with your pressing tool. Use a pointed tool to press the lines into the clay to depict closed eyes. The lines should curve up slightly at the edges, like a slight smile. You can continue adding very small amounts of clay as you go to fill in any spots that don't appear to have enough dimension, and then use your clay tools to refine them.
Create the baby's mouth. Roll two very small "snakes" from your clay, but make them wider than the mouth will be. Place them slightly below the nose, and use the clay sculpting tools to shape them into lips. If you find the baby's face is too narrow, continue adding equal-sized rounded bits of clay to the cheek areas and chin, until you have produced a convincingly round baby's face.
Create ears for the baby's head. Roughly sculpt two small shapes for the ears, and use the sculpting tools to attach them to the sides of the baby's head, smoothing them with your tools and fingers. Use a sharp tool to create the indentations in the outer ears.
Create the torso of your OOAK baby. Take the larger ball of foil, and wrap it in polymer clay of the same thickness as that of the baby's head. Smooth out the seams. Use a small sharp tool to form the belly button about two-thirds of the way down the torso. Gently work your wire into the bottom of the baby's head, and then gently press the other end into the top of the torso, taking care not to press too hard on the softened clay so you don't dent the baby's head.
Roll a "snake" of clay to form the neck. Remember, most babies have short, chubby necks. Wrap the clay around the armature wire between the baby's head and torso, and smooth it into a neck with your sculpting tools. Use a sharp tool to place little horizontal lines in the neck so that it is not perfectly smooth.
Roll four more snakelike pieces of clay for the arms and legs. The legs should be thicker than the arms. Use a sculpting tool to make the hand shapes, fingernail lines, foot shapes and toenail lines. Make bends in the shapes where the elbows and knees should be located. Attach the arms at the shoulder area of the torso, using the sculpting tools to smooth the edges. Attach the legs in the same way to the hip area of the torso. Remember, this is a baby, so you can bend the legs up and in close to the torso or lay them out straight, as if the baby is sleeping stretched out. Arms can be bent so that a hand touches the baby's face, or an arm is folded across the torso.
Smooth out the entire sculpture using your fingers and clay tools. You may wish to use more clay to place a diaper on the baby, or use your tools to sculpt the genitalia, choosing the sex you want your baby to be.
Preheat your oven to 230 degrees Fahrenheit. Place your baby on a bed of polyester batting, and place in a ceramic baking dish. The batting will keep the baby from getting shiny spots where the clay touches the pan. Place the baking dish on the preheated oven's center rack. The time required to bake polymer clay of one-quarter-inch thickness is about 30 minutes. You can bake it longer if you feel it is necessary, but remember that over-baking can discolor lighter clays, so watch it carefully.
Once your piece is finished baking, let it cool overnight, then use fine-grained sandpaper to smooth out any edges or flaws you see in the piece.
Use your pink paint and brushes to add pink highlights to the baby's cheeks, lips, and other areas. To get a more natural look, dip the brush in the paint, and then blot most of the paint on a paper towel before applying the brush to the baby's features. Your OOAK baby will begin to take on more life as you highlight and finish it with paint.