Intermediate to Experienced: crochet provisional cast on, unusual construction

Key-hole style scarf

Finished Measurements
Width at neck: 6in/15cm.
Width at bottom of scarf: 8in/20.5cm.
Length: 55in/140cm.

Yarn
Knitted with 1 x 100g skein of Luci shade 09 Andesine.

Needles and notions
Size US 6/4mm circular needles, any length. Size US G/4mm crochet hook.
Waste yarn.
2 stitch holders.
1 locking marker (optional.)

Tension/gauge
20 sts and 38 rows to 4in/10cm over garter stitch.