Scallop Shell knit pattern. Two color Slip Stitch Knitting. Includes text and video tutorial

Color A, cast on a multiple of 10, + 9 sts.
Rows 1, 3, 5, 7 - RS: Color A, k2, * sl 5 wyif, k5; rep from * to last 7 sts, sl 5 wyif, k2.
Rows 2, 4, 6, 8: Color A, purl.
Row 9: Color B, k4, * k1 uls, k9; rep from * to last 5 sts, k1 uls, k4.
Row 10: Color B, purl.
Rows 11, 13, 15, 17: Color B, k7, * sl 5 wyif, k5; rep from * to last 2 sts, k2.
Rows 12, 14, 16, 18: Color B, purl.
Row 19: Color A, k9, * k1 uls, k9; rep from * to end.
Row 20: Color A, purl.
Repeat Rows 1 - 20.

Knitting abbreviations:
K: Knit | P: Purl.
SL wyif: Slip stitch purlwise with yarn in front.
K1 uls: Knit 1 under loose strands. Insert RH needle through the 4 strands from below, then knit next stitch bringing the knit stitch through the loops.