Yarn: Any worsted weight wool yarn, but model was created with Cascade 220. You'll need a 1/3 - 1/2 skein, depending on how tightly you knit.

Gauge: My garter stitch was about 16 stitches to 5 inches and about 20 rows to 4 inches. On US size 11 needles. But exactness is not critical as long as you don't knit too tightly or run out of yarn.

Needles: One set of size US 10-1/2 or 11 DPs

Instructions:

Cast on 16 stitches using either a standard cast on or an invisible cast on method. Using an invisible cast on will ensure a smoother bottom edge, but requires scrap yarn.

Bottom
• Knit 9 rows
  
• On the 10th row, knit, increasing one stitch in every stich so that you have 32 total stitches.
  
• On the 11th row, (K1, slip 1 to alternate needle held in front of the work)* to end of row. When the row is finished you should have 16 stiches on your primary needle and 16 stitches on the auxiliary needle.
• Switch to the new set of stiches, Knit in stockinette stitch until ~1/2 - 1 inch below desired height of bag. Bind off loosely.
  I knit 4 inches. This is the center partition for the bag.
• return to stitches on primary needle. Continue in garter stitch until you have 20 rows total.

Body
• Knit 16 stitches and leave on 1st needle.
  Pick up 10 stitches on adjoining side of rectangle, corresponding to the garter stitch ridges and leave on 2nd needle.
  Pick up 16 stitches on cast on edge and leave on 3rd needle.
  Pick up 10 stitches on remaining short side of rectangle, corresponding to the garter stitch ridges. Leave on 4th needle.
  There should now be 52 stitches on the needles, and the partition should be pointing up through the square formed by the needles.
• Working in the round, purl all stitches in the first round. Don't do anything with partition.
• (Knit front 16 stitches. Switch to short side. Knit 5 stitches.
  Increase one stitch by picking up stitch in between the first and second edge stitches in the bottom/base row of the partition. Knit the remaining 5 stitches on the first short side.)* Repeat to * 1 time. There should now be 54 stitches on the needles.
• **(Knit front 16 stitches. Switch to short side. Knit first four stitches. K2tog. Pick up stitch from partition as described in previous instruction line. Knit remaining 5 stitches). Repeat process for back and second short side.)**
• Repeat from ** to ** until partition has been fully attached to the sides.

Shape Top
• K16, K4, K2tog, K5, K16, K4, K2tog, K5. There should now be 52 stitches across the 4 needles.
• K16, SSK, K6, K2tog, K16, SSK, K6, K2tog. There should now be 48 stitches across the 4 needles.
• K16, SSK, K4 K2tog, K16, SSK, K4, K2tog. There should now be 44 stitches across the 4 needles.
• Purl 44 stitches (one round).
• Loosely bindoff 16 stitches. K4, K2tog, K16, K2tog, K4. There should now be 2 needles with 5 stitches each and 1 needle with 16 sitches.

Strap
• Turn knitting, knit 5.
• Knit in garter stitch (K every row) for 12 inches.
• Graft these 5 stitches to 5 stitches on opposite side needle, being careful not to twist strap.

Flap
• Join yarn back to flap and knit in garter stich for about 4 inches.
  For a smoother edge, you may want to slip the first stich of every row purlwise
• Rows 1, 3, 5: slip 1, SSK, knit to last 3 stitches, K2tog K1
• Rows 2, 4, 6: slip 1, knit to end
• Last Row: SSK, bind off firmly to last 2 stitches, K2tog, bind off.

For a wider flap, increase 1 stitch at each edge of the flap after joining yarn. The garter stitch narrows a lot more than you think it will, so it may seem too wide but the felting process will take care of it. Weave any remaining ends in loosely and felt in washing machine. I recommend felting this down hard so that any edge seems fade into the fabric.

Allow to dry. I wrapped two decks of cards with plastic baggies and stuck one deck on each side of the partition. Pull flap into desired shape. Flap may need to be steamed to get desired shaping.