All you need to do is assemble the ingredients and get your cookware together.
Bring the stock to a simmer in a large saucepan.
In a separate saucepan, melt the butter over low heat (don't let it burn) and add the flour. Raise the heat to medium and stir the butter and flour together for about 2 minutes.You are making the roux. Take a good whiff and it should have a pleasant toasted smell.
Whisk the simmering stock into the roux and keep heating and whisking.
When the stock begins to simmer again, turn down the heat to low and cook until the sauce thickens. A thin skin may form, just skim it away with your spoon.
Depending on your stove-top, the sauce may take 5 - 10 minutes to get to your desired consistency.
Season with salt and pepper
Strain if you have a fine mesh strainer or chinois.