A baby bunting is any article of baby clothing that has armholes or sleeves, but only one pocket for the legs. It's great for keeping your baby warm and comfortable at night, as it is effectively a blanket he cannot kick off. Baby buntings are simple, quick sewing projects, even for beginners. You can make a simple, minimal-sewing baby bunting in about an hour.
Rip the seams out of the sides of the old pajamas: the shoulders, sides and down to the feet. Snip the front half of the pajamas in half from neck to crotch, with any fasteners fastened. This will be your pattern. If you don't want your bunting to have sleeves, remove them as well.
Pin the front halves and back of the pajamas flat to the fleece with the weave, right side out, to the right side of the fleece. If the fleece is patterned, pay attention to how the pattern looks. You don't want upside-down duckies or princesses.
From the portion waist-up, cut the fleece about 1" outside of the pajamas all the way around. From waist down, cut straight down, perpendicular to the shoulders, to about 4 inches below the lowest part of the pajama pattern if it has feet, 7 inches below if it does not. Adjust up or down if you want a bit more room for your baby. Cut the edges more generously if you want a looser-fitting bunting.
Ignore this step if you do not have sleeves in your bunting. For sleeved buntings, pin the shoulder and top arm portions of your bunting, right sides together. Hand or machine stitch these seams. Cut your ribbing in half so that you have two 6-inch pieces.
Gently stretch and pin the ribbed material to the end of the bunting sleeve, right sides together, to form a wrist cuff. Keep the ribbing tight enough to be snug but not too tight. Cut off any excess.
Pin your bunting parts in preparation for sewing, right sides together, paying close attention to how graphics on the fleece will appear in the finished product. Hand or machine stitch the front parts of the fleece to the back part; overlap the right front half over the left front half where they meet at the bottom. This stitching does not have to be perfect, as fleece is very forgiving, but it should be tight so that there is no chance of little toes or fingers getting caught between stitches. The seam allowance should be just over a half-inch.
From bottom to top, stitch the front opening of your bunting together to about waist level, overlapping the right side over the left. Turn your bunting right side out. Securely stitch hook-and-loop fasteners to the sides of the remaining opening, making sure they meet evenly when the opening is closed. (Because it is fleece, front edges do not have to be folded in, but you can fold them under to make a hem if you wish.) If you wish, you can stitch another length of ribbed material to the neck hole of your bunting to keep it snug against drafts.
If you're going to use your baby bunting in a stroller or car seat, snip a 3-inch horizontal slit in the center of the bunting's front and back, about 6 inches or so from the bottom, to thread the center strap through. A bunting made of fleece will not ravel, so the cut does not have to be hemmed or finished to prevent raveling. A slit this small will not let in significant air, but you can attach hook-and-loop fasteners on them if you wish.
Attach any decorations: appliques, nondangly trim, pockets, monograms or anything else you would like to have on your baby bunting. Stitch securely so your baby cannot pull or suck anything off. Use only cloth decorations. Beads, googly eyes, strings and other hard or nonflush decorations can pose a hazard.