Add whatever vegetables you have on hand to make the stock.
Add more water if desired to make more stock. Just add more vegetables so you get a flavorful stock.
You can use dried herbs if you wish. The one herb that I use in small (as opposed to large) amounts is Rosemary. Rosemary can add a strong flavor so I use it, but I use it sparingly.
Freeze the stock in ice cube trays to use for sauteing vegetables. You can also freeze it in larger containers for use in soups or sauces.