Yesterday I was in one of those hip baby boutiques, and these doll carriers were thirty-four dollars! I stood in the store for 20 minutes, handling it and eyeballing it, until (lightbulb!) - I figured out how to make it. $34.00 saved.
Doll-sized sling: cut one piece of fabric 20" by 8"
Child-sized sling: cut one piece of fabric 42" by 16"
Two D-rings of any size (optional - you could skip this step and just sew the ends closed)
Edge all four edges of the fabric by folding over twice and stitching in place.
Pleat both ends to appx. the width of your D rings and stitch to hold the pleats in place.
Once both ends are pleated, the middle fans out like a hammock to hold the doll.
Slip both D rings on one pleated end
Turn the pleated end under to the wrong side of the fabric and stitch in place.
Thread the other pleated end through the D rings to secure. Adjust the length to fit your child/doll.