First cut a piece of fabric 20 * 25 cm.
Now put a ribbon on the fabric with overlap of about 5mm and sew.
From the other side sew a ribbon on a zipper.
Now fold the cosmetic bag in half from the wrong side and sew the other edge of the zipper with the free edge of the fabric.
Cut off the extra part of the zipper. Sew the side edges of the bag. First unzip the zipper so that later you can turn out the bag. Now turn out, the makeup bag is ready!