Can you do shirring with elastic thread? If so,
Cut two rectangles of fabric, as long as you want the dress to be plus hemming.
And each piece will be your bust/2+10" or add more or less " depending on how much gathering you want. Hand wind elastic thread on the bobbin. Sew rows of stitches about an inch down from top and at 1 inch intervals down as low as you want (usually a few rows under the breasts). Add straps and hem top and bottom! Voila! Nice shirred full skirted sundress!!
Like this!