Fleece is a non-woven product which means the edges won't ravel. When using fleece for a blanket, most manufacturers use a blanket stitch around the edges, just for decoration. However, most of us don't have a blanket stitch on our machines or, if we do, it's not as big as the commecial ones.
My suggestion, if time is short, just do a straight edge or use pnking shears. If you have time you can hand-stitch a blanket stitch (ouch!) or, pick up about half-yard to contrasting fleece and make a binding for the blanket as you would for a quilt. Good luck. I love fleece!