Cut the fabric pattern
Measure the template by tracing around the paper pattern you have drawn; cut out two pieces of body fabric: outer body fabric and interior body fabric. Cut out a small strip at the bottom of the interior fabric. Do the same to cut out two rectangles in picture 3. Place the outer fabric with right side down; fold the up right angle.
Cut the interior rectangle
Lay the outer rectangle with right side down; fold the up right angle. Mark the edges of the interior rectangle with the middle bottom unmarked. Cut out the unmarked place.
Overlap the two pieces of body fabric
Do the same as step 2 to cut out the interior body fabric. Cover the interior body fabric on the right side of the outer body fabric. Adjust the two pieces of fabric; make them well aligned.
Sew two pieces of body fabric and rectangle
Align the two pieces of body fabric; trim the edges of the two pieces; back stitch the edges of the body fabric. Seam the two pieces of rectangle fabric in the same way. Place the body fabric with right side down; fold the left semi-circle.
piece the whole bag structure
Fold the right semi-circle. Sew the junctions of the semi-circle and rectangle below at each corner. Divide five parts at each side of the semi-circle; make marks. Place the rectangle fabric on the body fabric; make layer with one side at marked 2 and the other side at marked 4 as it is shown in picture 4. Sew the two corners of marked 2.
Sew the bag structure
Sew the two corners of marked 4. Note to flatten the marked 4 fabric before you fix it through stitch. Then the basic bag structure is done as the picture 3 shows. Fold the outermost rectangle body fabric to the marked 1; adjust a right angle at both sides; sew the shapes.
Sew a snap-fastener inside the lower middle of the front cover; match the other snap-fastener on its body fabric. Sew a cotton label on the place where you sew the snap-fasteners.