As promised, here is my tutorial for making a messenger bag. Lots of photos, and hopefully directions you will be able to follow, but if I've not made anything clear, just leave me a comment and I'll try to help.
As a reminder, here is my bag:
To make this bag, you will need the following fabrics cut out. I have labelled each side with a letter so that you can adjust this bag to whichever size you want. I think perhaps you could also make it into a laptop bag by incorporating batting between the layers. Side pockets are optional, pin them to the side pieces before you begin sewing the bag together.
I have used a heavy-weight fabric. If you are using a light-weight fabric, you may need to use interfacing.
Sew the side pieces to the long edges of the front piece, right sides together. Use whichever seam allowance you prefer, but stick to the same seam allowance through the whole pattern. I used 1/2". Sew bottom piece to short edge of front piece, right sides together. Then sew the back piece to the other side of the bottom piece. You should end up with a shape like this:
Now bring the back up and sew the sides of it to the side pieces. This makes the basic bag shape.
Open out the bottom corners and sew across them (where the pins in this photo are).
Turn your bag in the right way.
Add applique to the front of the flap piece. I made a flower and used free-motion embroidery to attach it to the bag in the top photo. For the bag I made for the tutorial, I added a felt heart and blanket stitched it around the edge. Let your imagination run wild here!
If you are using a fastener for your bag, add it to the centre of the flap lining piece now, about 2" up from the edge. Place flap pieces together, right sides together, and sew around the edge - leave a 2" gap at the top of the flap to turn in the right way.
Turn it in the right way and then top stitch along the edges of the flap.
Add your chosen fastening to the front of your bag. It must line up with where the flap will end up. I pinned the flap in position to check where the fastening should end up.
Now make the lining of the bag by placing the front and back right sides together and sewing down the edges and then along the bottom of the pieces.
Open out the corners and sew across them.
Leave the lining the way it is, and place it over the top of the bag (which should still be the right way out) and sew around the edges. Again leave a 2" opening so you can turn it through.
Pull it through the gap now & then top stitch around the edges of the bag.
Place the flap in position on the back of the bag and stitch it down, make sure the fastenings join up.
Take your two small rectangles and hem both short edges with a small hem. Fold long edges to centre and sew down each side.
Enclose D-ring in the centre of the strip and sew both ends to the side of the bag.
Repeat for the other small rectangle.
Now make the strap. Fold both short ends over a small amount and then fold the long edges to the centre of the strap. Fold the whole thing in half length ways enclosing the raw edges inside.
Topstitch down each edge of the strap to make it look nice.
Put the handle through the D rings and sew it in place. I used a slider to make the strap adjustable, but that is entirely optional.
This is how my bag turned out.
Anyway well done to those people who made it through a marathon post. Hope it helped show you how to make a messenger-type bag.