Can I just put them in a jar with a bow on it?
Biscotti need to in an air-tight containers.
For room temp, jar with a bow or a decorative tight-seal tin is good.
For freezer use, consider a glass jar with a tight plastic lid (e.g. wide-mouth mason jar with one of those white plastic lids sold as accesories or any of several branded plastic freezer storage boxes).
sure. for fancier, you could stack them in a tall narrow 'candy bag', tied w/ a pretty bow.