You can get the Free Pattern HERE
You will also need:
1/2 yard of fabric.
8" of 3/4" Elastic.
Cut the pieces as instructed on the pattern. The straps may be cut on the bias if you like, but depending on the fabric this may make the straps stretch out longer so be warned.
Sew with 3/8" seam allowance.
Then hem the bottom and you are done.
Shorts || Old Navy