Cutting:
From Bag fabric, cut the following pieces:
Bag: 25 ½” x 16 ½”. The center width of the bag is 16 ½”. Taper the sides in 1” from the center to each corner. The lower edge will be 14 1/2”.
FlapBack: 12 ½ x 14”
Flap Front Top: 4 ¾ “ x 14”
Flap Front Bottom: 8 ½ x 14”
From Lining fabric, cut the following pieces:
Lining: Cut 2--13 x 16 ½ ”. Taper in 1” from the top edge to the bottom edge. The bottom edge will measure 14 ½ “
Flap Lining: 12 ½” x 14”
Pockets: Cut 2 –8” x 10”
Interfacing:
Cut one Bag piece following above instructions for bag.

Hint: Label pattern pieces with a sticky note or masking tape

The corners of the lower edge of the flap are diagonally shaped. Trim diagonally 1 ½ from each corner on one long side (the lower edge) of the following: Flap Back, Flap Bottom, Flap Lining. 

Steps:

Unless otherwise indicated, use ½” seam allowance

1. Interfacing: Trim 3/8 “ from interfacing seam allowances. Fuse interfacing to bag following manufacturer’s instructions.
2. Pockets. Clean-finish top edges by  pressing under ¼” to wrong side.    Stitch close to the folded edge. Fold clean-finished edge ¾ inch to the right side; pin. Stitch 5/8 inch along side and bottom edges, backstitching at upper corners .  Trim upper corners. Turn pocket tops right side out; press.  Press  side and bottom edges under along stitching lines. Topstitch 5/8 inch from top fold of each pocket.

3. Attaching Pockets: Place Bag Pocket on the right side of the Bag, 4 inches from the top edge (1); pin.  Place Lining Pocket on the right side of the Lining (2); pin. Stitch side and bottom edges of both pockets close to the edge; backstitch at the upper corners (1,2).
Mark center line on bag pocket. Stitch from bottom to top. Divide one side in half again and stitch from bottom to top to create pencil dividers(1). (Sew from bottom to top of the pocket to avoid a pucker at the bottom of the pocket.)

4. Flap. For Flap pocket,  fold ½ inch under along the 14” edge of each of the Flap Front Top and Bottom  pieces.   Pin zipper in place. Stitch close to the edge using a zipper foot. Pin Flap Lining to Flap Back, wrong sides together. Pin Flap Back and lining to Flap Front,  right sides together. Stitch leaving the upper edge open. Trim and grade seam allowances. Turn right side out; press. Top stitch ¼ inch from side and bottom edges.
Place Flap on right side of Bag at the opposite end from the Bag Pocket; pin.  Machine-baste ½ inch from the edge (3).

5. Bag & Lining. Place Lining piece with the Pocket over the Flap end of the Bag, right sides together; pin.  Pin second Lining piece to the other end of the Bag.  Stitch, as shown (4); backstitch.  Trim seam allowances; press open. Fold Bag and Lining right sides together; pin (5).  Stitch, starting and stopping 3 ½ inches from the corners of the Lining; backstitch and trim. Mark a fold line on the interfacing at bottom of Bag.

6. Corners:  For bag, form the square corners at the bottom of the Bag by clipping the seam allowance to the stitching (5).  Form a triangle at each corner by pinning the side seam to the fold line.  Mark 2 inches from the point along each edge.  Stitch between the markings ; backstitch. For lining, pin side seam to the bottom seam; stitch across the triangle 2 inches from the point.

7.  Turn Bag right side out.  Stitch the opening in the Lining closed. Top stitch around the opening of the bag ¼ inch from the edge.

8. D ring Loop: From webbing cut one piece 4 ½”. On one end fold under1 inch of webbing. Insert  2 D-rings pushing the flat side of the rings against the fold.. Stitch ½ inch from fold to secure D-rings in the loop.  Fold the remaining raw edge of the webbing until it touches the edge of the first fold.  D ring loop should measure 2 inches. Place loop over one side seam that the folded edge with the D-rings is slightly above the top of the bag edge. Stitch in place securely with a X-inside a 1 inch square box.

9. Strap: Using remaining webbing fold under 1 inch. With fold pointing toward bottom of bag, center the strap on the other side seam. Stitch strap in place 2 inches from the top of the bag. To finish strap edge turn down ¼ inch of the raw edge of strap, stitch. To adjust the strap, slip the end through both D-rings, then between them. Pull to the length desired.