What you need:
- 24" x 11" lightweight fabric
- matching thread
- elastic thread
Use a lightweight fabric and cut (or better rip, that will make it perfectly straight and square) three squares with the following dimensions
24" x 9" (dress)
2 pieces of 5 1/2" x 7/8" (straps)
1. Double hem the two long sides (3/8" wide)
2. Then comes the elastic shirring (see below for info)
3. Go in rows about a 1/4" apart, start 1/4" from the top
4. Make about 9-10 rows ( until you are about 2 1/4" down from the first shirring row)
5. Sew back together being careful to line up the rows as good as possible
Don't be surprised if it is still a little too wide. Hold an iron with steam over it and the fabric will loosen and with that it will pull it tighter.
6. Take the 2 pieces of fabric (5 1/2" x 7/8") to make the straps
7. Create the shoulder straps like double folded bias tape 1/4" wide
(fold both sides half way in then fold in the center)
8. Sew on shoulder straps
Find center front, mark, measure about 1 1/4" from either side of the mark, sew on
Measure about 1 1/4" from either side of the back seam and sew on
You are done !!!
Make a 22" bias tape fold in half and attach in center front and tie behind the neck. That way it will be like a V.
Info on elastic shirring
you can find a lot of info on elastic shirring on the web. One good tutorial is here
Elastic Shirring tutorial