Quilted Lattice Slip Stitch Pattern

How to knit the K1 under loose strand.
Take the right-hand needle under the slipped thread, then pick up the next st on the left-hand needle and knit this st and the slipped thread together.

Pattern
Cast on a multiple of 6, +3.
Row 1 (RS): K2, *slip 5 wyif, K1; rep from * to last st, K1.
Rows 2, 4, 6 and 8: Purl.
Row 3: K4, *K1 under loose strand, K5; rep from * to last 5 sts, K1 under loose strand, K4.
Row 5: K1, slip 3 wyif, *K1, slip 5 wyif; rep from * to last 4 sts, K1, slip3 wyif, K1.
Row 7: K1, *K1 under loose strand, K5; rep from * to last 2 sts, K1 under loose strand, K1.
Repeat rows 1-8.