A perfect pattern for yarn oddments is the crochet pattern for the infinity scarf "Stephanie".
The cowl is crocheted in the Moebius-technique. You will have fun from the start on because there is no chain counting and no foundation crochet.
according to your desired size of the cowl approx. 400 - 1000 metres of e.g. a yarn cake such as Sheepjes Whirl or yarn oddments
crochet hook size 3 – 4 mm (metric size, please use google to determine your hook size)