You can of course use any fabric, I just stayed with the same name as the purse I posted in Pictures (even though I did use another fabric for this tutorial). I hope it doesn't seem complicated, I tried to make it detailed, hopefully I haven't made it unnecessarily complex. It is long though so I may have to break it into two posts.
2 fat quarters or half yard for exterior
2 fat quarters or half yard for lining
About 1/2 yard muslin
About 1/2 yard of high loft poly batting
Piece measurements for Exterior and Lining:
Body: 16 1/2" L x 10" W
Sides (2): 6" L x 4 1/2" W at bottom, 3 3/4" W at top
Flap: 9" L x 10" W (including 1 1/2" curve from end of straight sides to top)
Pocket: 5" L x 10 1/4" W
Button Closure (lining fabric): 5" L x 1 1/4" W
Strap: Outer fabric - 34" L x 2" W, Lining fabric - 34" L x 1 1/2 W, Batting - 34" L x 2" W
Use larger pieces of muslin and batting for body, sides and flap as you would in typical quilting, extending an inch or two from fabric edges.
Pocket batting piece should be scant 1/2" narrower than pocket fabric pieces (as you will slide batting inside once top and bottom seams are sewn). Allow batting to extend out on either short side about an inch as for typical quilting.
The body of the exterior and lining are simply rectangles 16 1/2" L x 10" W, you probably don't need a pattern piece for this, cut on your mat with ruler. The other pieces can be cut from printing paper or any other clean sheet of paper. The Flap has a curve at the top that extends up 1 1/2" from where the side goes into the curve (see picture). Cut a piece of paper 9" x 10", fold in half lengthwise, mark 7 1/2" on the long side, draw or cut a smooth curve to the fold. The side pieces are narrower at top than bottom, cut a rectangle of 6" x 4 1/2", fold in half lengthwise, on one end measure 1 7/8 (the little line just before the 2 inch mark on most rulers), draw a line from bottom edge to mark, cut, unfold and check to see that the top is 3 3/4 inches wide, bottom should remain at 4 1/2" wide (and the sides are 6" L. The pocket is another rectangle of 10 1/4" L x 5" W, button closure (of lining fabric only) is 5" L x 1 1/4" W. I don't make a pattern piece for the strap, if you're working with fat quarters, cut two 2" pieces on the 18" L side, sew together and trim to 34" L, do the same for the lining fabric except 1 1/2" W and 34" L. Here's a pic of my pattern pieces on fabric so you get a visual idea of them and the layout I usually use with fat quarters:
And with yardage:
Press closure (lining) fabric in half lengthwise, unfold and press while aligning long edges with center press line, fold in half lengthwise, press and pin, sew down long seam, topstitch the other (fold) side. With closure looped, check against button to be sure closure loop isn't too large, pin ends together where it needs to meet flap seam so it fits over button but not too loosely.
Sandwich body with batting and muslin (I use spray basting to hold layers together), along top and bottom edges with ruler and chalk mark every 1", quilt wavy or straight lines from bottom to top marks. Fill in sides an inch apart if wavy, sew down side fabric edges if straight lines. Repeat with flap. I use two layers of poly batting for the sides for extra sturdiness but you can use one layer if desired. Quilt sides, repeat as with body on side edges. Trim and square up all pieces as necessary. Trim bottom (raw edge) of flap to 8 1/2" L from top center of flap to raw edge. If you like a shorter flap, trim a bit more, in batik purse it measures 8" from sewn seam to top center.
Once exterior body, flap and side pieces are quilted, lay pieces on lining fabric and trim lining as necessary to same sizes.
Place side pieces with bottom edges at the raw edge of body in center of body, right sides together, measure from side piece corner end to body end on both sides to center sides, pin and sew 1/4" seam on side piece bottom, leaving a scant 1/4" unsewn at beginning and end of seams, backstitching at each end. Matching top raw edges pin and sew seams along each side, easing in the body corners (or clip body almost to seam at side fabric corner to help it lie flatter) and sewing just inside the bottom seams. Once all four side seams are sewn, trim top edges to even up if necessary. Turn exterior right side out.
Fold flap lining in half lengthwise, mark midpoint at top, place exterior and lining fabrics right sides together, place pinned/looped closure between exterior and lining fabric with closure's raw edges just outside fabric raw edges, pin so closure ends remain crossed over (remove previous pin on closure), sew flap together around outer edge with 1/4" seam, leaving bottom raw edges unsewn, clip curve along top and trim seam, turn right side out, press lining side.
Quilted pieces and closure: