Flouring meat for a stew is a convenient way to thicken the gravy. This tends to work best if you brown the meat with the flour on as it gets the flour properly cooked.
The downside is that it makes it harder to get good caramelisation on the surface of the meat without burning the flour, although for slow cooked stews etc. This is rather subjective and comes down to personal preference.
If you aren't going to brown your meat it may be more convenient just to add a roux (which you can make in bulk and chill or freeze to use as needed). This is better than flouring the meat as the flour in a roux is pre-cooked. You need a fairly high temperature to trigger the chemical changes in the starch which makes it thicken the sauce and slow cookers might not reach that temperature. That would give the dish a raw flour taste and won't work as well as a thickening agent as a roux.
A basic roux is also the base of many sauces and very easy to make.
Some cuts of beef like shin and oxtail produce a perfectly good sauce without flour, especially when slow cooked.
There are also plenty of other thickening agents. I quite like pearl barley in beef stew but peas, lentils and potatoes also work as does tomato paste, but that has a significant impact on flavour (not bad but not necessarily what you want). There are also various flavour-neutral thickeners.
Also, adding a starchy staple near the end of cooking such as rice, pasta, noodles or part-cooked potatoes will thicken the sauce and make a complete one-pot dish.
A thick gravy in stew tends to bring the flavours together well but a thinner broth-like sauce can work as well, especially if you like quite punchy Asian-style flavours.