Cut out a rectangle 36" by 14" out of the cover fabric. Cut one of the 14" long sides in to a rounded edge.
Pin the cover fabric, wrong side up, on to the lining fabric. Cut out the lining fabric to the same shape as the cover fabric.
Sew the cover and lining fabric together, leaving a small gap so that the fabric can be folded inside out and then sew up the gap. Fold the bottom edge of the fabric up so that the rounded edge falls over like a flap. Take two points in the middle and pin along these to make the bottom of your bag.
Sew along the two middle lines that you marked along earlier, removing the pins as you go.
Repeating step 1, cut out a rectangle of cover fabric the width of the lines you sewed out earlier and the height of the edge of the bag, pin this to the lining fabric and cut the lining fabric out too.
Repeating step 3, sew around the cover and lining fabric and then turn inside out. Make two of these.
Repeating step 1 and 5, cut out a square of cover and lining fabric about 6" by 6" for a pocket for the front of the bag.
Sew the cover and lining fabric together and fold inside out.
Fold the flap over and then pin a buckle strap to the flap and the front of the bag.
Sew the bottom part of the buckle strap to the front of the bag.
Take the pocket that you made earlier and lay it lining side up.
Fold in the two edges.
Sew this to the front of your bag.
I also cut a square and flap out of clear vinyl and sewed it on to the front of my bag to make a clear pocket.
Now is the time to pin the sides of the bag to the main part of the bag, one side at a time, starting with the side without the flap. Sew along each edge.
Now sew the top part of the buckle strap to the flap.
Now cut a very long strip of fabric for your strap.
Fold it in half so that the wrong side is facing up and pin along the edge. Sew along the edge and then fold inside out.
Repeat the previous step with a shorter piece of fabric and then slip a D ring in the middle and sew this loop to one side of the bag.
Sew one end of the other fabric strip to the other side of the bag. Slip the other end through the D ring.
Slip this loose end through a strap adjuster and stitch down the end of the other side.