Eyelet lace knitting stitch
A yarn-over paired with a decrease creates an opening while preserving the stitch count.
Counted practice swatch
Cast on 22 stitches: a multiple of 4 plus 2 edge stitches.
Work the repeat
Row 1 (RS): k1, [k2, yo, k2tog] 5 times, k1. Row 2: purl 22. Row 3: k1, [yo, k2tog, k2] 5 times, k1. Row 4: purl 22. Repeat.
Read the fabric
Each yarn-over adds one and each k2tog removes one. If the count grows, look for an omitted decrease beside the eyelet.