Turn bag right-side out.
Cut two 3 1/2" strips from around the top of the bag. These will be the handles.
Zig-zag the cut edge of the top. Fold down 2" all around and sew.
Cut the handle strips 20" long and hand press 1/4" to the inside on both long sides. Fold in half and sew down the long side.
Attach the handles to the bag as shown.
And now you have successfully recycled a feed sack into something useful!