A pattern isn't really necessary, but here's how I made the belt. I chose the hemp cord for its color and texture. Other thick or textured yarn can be used.
by Mimi Alelis, © 2013
Crochet hook size 4mm
Button for closure
Row 1: Leave enough tail of yarn for sewing-in the button later. Ch 4, dc in 4th ch from hook, turn.
Row 2 onwards: (Ch 3, dc on top of ch 3 of previous row, turn) repeat up to desired length of belt, then ch 5 or 6 (or chain just enough to fit the button), sl st on same row, fasten off.
Finishing: Sew button at the 1st row. Weave in ends securely.