For health reasons, the current trend is to make sauces by reduction and without flour. This is done by reducing 300 ml/10 fl oz/1¼ cups of wine, stock and flavourings to only a few tablespoons of liquid. The sauce may then be thickened with 1 tablespoon of double/heavy cream.
In my view, you might just as well use some butter in the first place; quite often it is used anyway, to sweat the vegetables in. As trends go, making sauces by reduction has its pros and cons. The value is that it generally makes a lighter and better-flavoured sauce than a flour-based one.