So the exterior of the bag is done so on to the interior. First up is the Zippered Divider Pocket.
Zippered Divider Pocket:
2 9x15 zippered divider pocket pieces
Lay one divider pocket piece right side up. Centre the zipper along one 15" side and line up the edge of the zipper fabric to the raw edge of the pocket. Sew along the edge with a 1/4" seam. Lay the piece right side up and fold the zipper so it is also right side up which will turn the raw edges to the wrong side. Pin the fabric so it just touches the edge of the teeth. With a zipper foot sew along the edge of the teeth. One side of the zipper is attached. Now repeat these steps for the other side.
With the zipper attached lay the pieces flat with wrong sides together and pin. Sew a scant 1/4 inch seam along the three open sides. Clip the corners.
Unzip the zipper and turn the bag inside out. Press the edges and sew another slightly larger seam but this time begin and end about 1/4" from the stopper on the zipper.
Turn the pocket right side out and set aside.
Sew the lining of the bag the same way you sewed the exterior but don't attach the bottom yet. Leave the lining so the wrong side is facing out.
Place the Zippered Divider Pocket inside the lining placing the edge of the pocket centred along the uninterfaced channel of the Lining Sides. Pin and sew a 1/4" seam to attach the pocket inside the lining. Make sure to sew all the way along that edge, not only the part where the pocket is or your lining won't fit properly.
Now it should look like this.
Now attach the bottom of the lining the same way you attached the exterior bottom.
Assemble the Bag:
If you would like to add a sturdier bottom in the bag cut a piece of plastic to fit (I used one of those hard plastic sheets out of a binder) and place it in the bottom of the exterior. Slip it under the seam allowances to help keep it in place and the slide the lining bag into the exterior bag. Line up the side seams and pin the two bags together. I've made this bag three times so far and every time the lining ends up a little too long so don't worry if it pokes out above the top of the exterior bag. It's more important that the inside be smooth and fit snugly rather than those top edges meet exactly. Sew all the way around the top edge of the bag to hold everything in place and trim whatever excess lining is peeking out of the top.
Attaching the Top Trim:
If you would like you can add a magnetic snap to keep the bag closed. I finally did this on this last bag and I love the results, but it isn't necessary. Just attach it on the insides of the Top Trim pieces.
Open the Top Trim piece so it lays flat. Stand the bag up and slide the Top Trim piece over the bag so the raw edge of the Top Trim matches up with the top edge of the bag. Pin all around the top of the bag. It will look like this:
N.B. If you opted for the magnetic snap make sure the side where they are attached is not the side that you are pinning to the bag or else you will have little magnets on the outside of your bag.
Carefully sew a 1/2" seam all around the top of the bag. Pull up the Top Trim piece and turn the inside to the inside. Pin the inside of the Top Trim piece along the inside of the bag turning under approximately 1/2" to cover up your stitching line. Carefully top stitch all around the bag again and you're done!