Typically I like to strain the liquid through a fine mesh sieve before thickening so I have a smooth sauce, but the choice is yours (you can either do so right into a small saucepan, where you’ll finish the sauce, or add it back to the Dutch oven if you want to shred the pork and add it back to the sauce before serving). At any rate, skim some of the fat off the surface of the liquid and discard. Bring it to a boil while you whisk the flour with about 3 – 4 tablespoons of rosé until totally smooth. When the liquid is boiling, whisk the flour-wine slurry into it vigorously. Let it bubble away for a minute or two, then reduce the heat to medium-low or low to simmer for about 5 minutes, until thickened slightly. This doesn’t end up like a thick gravy, but rather a sauce with some body; if you want something more gravy-like just up the amount of flour, making sure to add enough wine to get a smooth and pourable paste.