Cut out 2 rectangular pieces of 8 inches X 14 inches and 1 inch wide and 4 inches long strip. Fold the strip from both sides, matching their edges in the middle. Again fold it into half lengthwise and sew along the fold to secure the fold.
Take any one of the large rectangular pieces and fold any one side twice along its width. Pin the sides to secure the fold. Take the sewed strip and pin the open ends of the strip under the fold of the large rectangular piece, right in the center of its fold.
Sew along the fold, along with the button loop and also fold twice and sew any one side of the other rectangular piece’s width. Now fold the loop to the outer side and sew over it once more. The button loop is now ready.
Place both rectangular pieces together with their wrong sides facing out and sew along the 3 sides, except for the sewed border sides of both pieces. At the bottom end form a triangle from the corner. Sew a straight line to separate the triangular part. Do the same for the other corner.
Cut off the raw ends of the triangular part for both sides. Now fold about 3 inches of the bag from the top mark the button placement and stitch the button on its place.