Remove the meat and vegetables to a platter and cover with foil to keep warm. Skim the fat from the surface of the gravy; then strain the liquid into a saucepan and bring to a simmer.

In a separate bowl, whisk together the flour and water until it forms a slurry. Add the slurry to the gravy, whisking continuously until thickened. Continue mixing as you bring the gravy to a simmer; it will thicken noticeably. Season with salt and pepper to taste.