To begin with, it's a good idea to start with your back pocket. If you wanted this to take a tablet pc you will want to pad this pocket more than I have and possibly add some quilting. Keep the extra batting out of the seam allowance though as this bag gets thick around the edges!
Start by sewing your lining and outer right sides together along the top edge of piece C, the back pocket. Turn right sides out and press and then top stitch. I used piping in my seam.
Next mark on the lining where you'd like your magnetic snap to go. I always wait until after I've topstitched in case it's too near and catches on my presser foot. If you're making this pocket for a tablet PC you'll want to use velcro instead.
Unfold your back pocket so you only have the lining layer and cut your holes for your snap. That's not something you want showing on the outside!
Insert your magnetic snap and put your pocket back together again. I like to baste around the outside and trim any uneven edges.
Next lay it on top of your outer piece A and baste into place. Sure you can skip the basting but there's a whole lot of layers going to be getting up close and personal soon and it's quicker and easier to machine baste then have to unpick and re-position.
If you're adding piping then add your piping to your back piece now.
Now match up your leftover washer from your magnetic snap and mark where it needs to go on piece A (now sewn to your back pocket).
Fit this other half of your snap.
Now take one of your main pieces A and matching the centres, start pinning your gusset piece D around the edges. You'll need to notch the gusset to manipulate it around the corners, just make sure you don't go through the seam allowance.
My pins are angled for me to pull them out as I approach them as I prefer this to sewing over pins. I've broken far too many needles this year alone!
Once you've sewn one side, flip the piece over and do the same for the other main piece. You don't need to leave a turning gap, just go all round the three sides.
You'll be left with an inside out outer. Mine's not particularly attractive as I use heavy felt stabiliser.
Turn your outer right sides out and pin and stitch your flap and straps onto the main bag within the seam allowance. Make sure that your strap isn't twisted, that's no fun trying to unpick it all and put it right when you're finished!
Now you're ready to finish this bag up.
Insert your bag outer inside your bag lining right sides together.
Match the side seams and top edges and pin well.
Turn the bag through the hole in the lining gently teasing it all through.
Press well along the top edge smoothing the lining down inside. I like to pin my outer and lining in place. Top stitch the top edge going around the entire top of the bag including over the flap and straps. This may be slow going and you may not be able to go around all of the layers, this is when a strong needle is a bonus!
So now, like all good construction engineers you should notice you've still got a part left over. Half a magnetic snap. This is not the most popular method of inserting snaps but I like to wait til I'm certain of the placement.
Try on your bag and see where your flap falls to naturally.
Keep that in place to your table then mark where the snap should go using your washer. Reaching through the hole in your lining use your seam ripper to cut your prong holes and insert your magnetic snap.
Press and pin the opening in your lining and stitch it closed.
Tuck your lining back inside your bag and you're ready to go!
I'd love to see anyone's photos if you use this tutorial, just pop me an email out or leave me a comment