Make a slip knot and place on one needle. Using the long-tail cast-on method, cast on 30 stitches. This gives a scarf width of about 15cm. Hold the needle with cast-on stitches in your left hand.
Insert the right needle into the first stitch from left to right, wrap the yarn around the right needle counterclockwise, pull the new loop through, and slide the old stitch off. Repeat across all 30 stitches. Turn and repeat.
Continue knitting every row — this creates garter stitch (horizontal ridges on both sides). Knit until your scarf measures approximately 160cm or until you have about 30cm of yarn left.
Knit 2 stitches, then use the left needle to lift the first stitch over the second and off the needle. Knit 1 more, lift the previous stitch over again. Repeat across all stitches. Cut yarn and pull the tail through the last loop.
Thread the cast-on and cast-off yarn tails onto a yarn needle. Weave through several stitches on the wrong side to secure, then trim. Block the scarf by dampening it and laying flat to dry for best results.