Gravy (advice needed)

[ChrisN]

I've been watching a few YouTube videos of these old Cajuns making they're gravy, which is all fresh. Nothing out of a jar, flour, etc .... First let me begin by saying I am no gravy expert. But the end results to these videos look like a pretty delicious but a "runny" gravy. My question is what's the most methodical way to thicken the gravy. I am assuming the answer would be flour but .... Does the flour need to be added prior to covering meat with water and cooking down or after it has cooked down. Thanks! Any other ideas would be appreciated.