Preheat the oven to 400°F and place a large cast-iron skillet in the oven to get hot.
In a shallow bowl, whisk the flour with the fennel seeds. Season the pork chops all over with salt and pepper. Dredge the chops in the flour, shaking off any excess, and transfer to a plate.
Carefully remove the hot skillet from the oven and place over a burner on moderately-high heat. Add the canola oil. Add the pork chops and cook until very browned on one side, about 3 minutes. Flip the pork chops and then top with the thyme sprigs and 2 tablespoons of the butter. Transfer the skillet to the oven. Roast until an internal thermometer inserted into the center of the pork chops reads 140°F, 5 to 8 minutes depending on the size of your chops. The meat will continue to cook as it rests.
Carefully remove the skillet from the oven and transfer the pork chops to a plate. Loosely cover with foil and let rest while you make the pan sauce.
Return the skillet to the stovetop. Add the chicken stock and cook over moderately-high heat, scraping up any brown bits on the bottom, until the liquid has slightly reduced, about 5 minutes. Add the grapes and the remaining butter and cook, stirring occasionally, until the grapes have softened and the sauce is thick enough to coat the back of a spoon, about 5 minutes more. Stir in the sherry vinegar. Season with salt and pepper.
Spoon the grape pan sauce over the pork chops. Sprinkle with flaky sea salt and garnish with fresh thyme leaves. Enjoy!