Greetings! Recently I was rushing to make some skirts for the kidlet and her "twin cousin" (born eight hours later), during the last naptime before going to visit them. It struck me that I could make a skirt the same way a pillowcase can be made, so I took a few photos to share the process:
Step 1 (not pictured) - get some fabric (remnants work for a toddler skirt - width of fabric x the length you want the skirt); get some knit for the waistband (about six inches wide x the circumference of the baby's belly when not really stretched (this leaves room for a seam as well as some growing)).
Step 2: take up a few pleats in the skirt to make it as wide as the waistband fabric when the waistband is stretched out. Pin them and then tack across the top on your regular sewing machine.
Step 3: oddly, no clear picture of the pinning - likely because it was a bear to do - but it's the same method shown for the basic sausage pillowcase here - roll up the skirt, pinning the waistband around the skirt-sausage; to be safe, I recommend pinning the skirt down away from the edge of the waistband, as shown here. Then serge along the seam: