I buy and cut up thin towels for these as thicker towelling is harder to stitch neatly. I cut towelling and flannelette (in kid's prints) 9 x 18 inches then trim the corners using a plate to round them. Then stitch around the pieces with right sides facing and leaving a gap of about 3 inches to turn them right side out. Press out the seams neatly and then top stitch around the edges, closing the 3 inch opening at the same time.
I stitched 10 this afternoon and prepared another 16 ready to stitch so I will stitch them when I have a few minutes spare. I can get 5 from each towel and then piece the leftovers to make more and use up the scraps so they aren't expensive to make and new mums we donate them to will love to have some new items for their precious newborns.