Cast On 26 stitches.
Row 1: P4, K2, (P6, K2) across to last 4 sts, P4.
Row 2 (RS): K2, * RT, P2, LT, K2, repeat from * across..
Row 3: P3, K4, (P4, K4) across to last 3 sts, P3.
Row 4: K1, (RT, P4, LT) across to last st, K1.
Row 5: K2, (P6, K2) across.
Row 6: P2, (LT, K2, RT, P2) across.
Row 7: K3, P4, (K4, P4) across to last 3 sts, K3.
Row 8: P3, LT, RT, (P4, LT, RT) across to last 3 sts, P3.
Repeat rows 1-8 until desired length. Bind off. Fold piece over, seam sides, and sew zipper into top opening. Line bag if desired.
LT = Left Twist. Working begind the first stitch on the left needle, purl into the back of second stitch making sure not to drop off, then knit the first stitch letting both stitches drop off the needle.
RT = Right Twist. Knit second stitch on the left needle making sure not to drop off, then purl the first stich letting both stitches drop off the needle.