These newborn fitted diapers have a scoop in the front for the umbilical stump. They were pretty easy to make, although I left out the elastic in the back, which I didn't think was necessary, especially if you use something stretchy like jersey. The one one the right is made entirely of jersey knit, but for the one on the left I used jersey for the inside and flannel on the outside. The overcast stitches along the front where the opening is for the pockets was a bit tricky, since I didn't have a serger, but doable. For the inserts: the one on the left is made with two pieces of flannel that can be folded into fourths, and the one on the right has a preemie prefold inside. Both diapers have held up well, but take longer to dry along the legs where the elastic gathers are, than prefold or flat diapers. The pattern is available for free in pdf format from The Nappy Network. This is the Shar's Newborn with Umbilical Scoop pattern.
I thought the organic wool recommended was a bit pricey, being imported from New Zealand, which is famous for their merino sheep- the softest wool there is. After searching a bit, I found another source here in the US. Marr Haven Wool Farm, although not certified organic, raises sheep organically and uses no chemicals in the wool processing. A 1 lb. sport weight cone of their merino-rambouillet sheep's wool is $34 and is enough to make 2 pairs of longies with some left over. I only made 1 pair, plus a hat for my husband and several crocheted baby socks, and I still have about half a cone left. This wool is creamy soft, with the natural lanolin still present. I found the natural (an off-white color) to be a bit softer than the gray.
Felted wool covers are the most breathable of all diaper cover fabrics. To felt, take a soft wool sweater, such as the one pictured here, which I found at a thrift store for $2, and wash in a hot water cycle. Then place in a hot dryer to dry. The fibers will shrink together and form a thick mat.