Sorry for the delay in getting this next step posted. Oh, the "best laid plans of mice and men" uh?
Today we will be working on boxing the corners of your bag. You should have already sewn down both sides of your bag, making a flat quilt look like a .. well, like a bag! :) I find this is the step when I get really excited about my bags because it is actually looking like a bag instead of just a layer of fabric. I can see the light at the end of the tunnel.
I have created a video for you to view for these directions, but I will say just a few things.
When marking your corners .. be sure you are measuring from the fold and from the stitching line. I used 3/4 of an inch for my measurement, if you want a wider bag, you can use 1" or a bit more. Just be sure that you stay atleast 1/2" from the binding of the outside pockets. You'll be able to feel the "bump" from these bindings. If you get too close to these, stitching the corner closed will be very difficult and you won't get a secure seamline.
After you have cut out the square for your boxed corners, you then pull the square open and flatten it. Then stitch it. I use a straightline stitch, and then go back and use a zig zag inside the seam allowance. You could use a serger instead of zig zag if you have one.
At this time you could also zig zag or serge your upper side seams. If you want to reduce bulk here, then you could alterantely using some fabric or seam binding and cover these raw edges with the seam open. It all depends on how "finished" you want the inside of your bag to be. I generally choose to zig zag these side seams.
Without further ado .. here's the video: