Combine the flour, salt, pepper, and dried herbs (sage, rosemary, thyme, fennel, garlic powder, onion powder, and ground mustard) in a large bowl. One by one, coat each piece of turkey in the flour mixture. Heat the oil and butter in an oversized Dutch oven, cast-iron skillet, or roasting pan over medium heat until the butter starts to sizzle (if using a roasting pan set it over two burners).
Working in batches if necessary, brown each piece of turkey on all sides in the oil/butter, being careful to not overcrowd the pan, continue with all pieces, about 5 minutes per side. Transfer to a plate while browning more pieces.
Add the onions, carrots, celery, garlic, rosemary, and thyme to the skillet and cook, stirring, until the vegetables begin to soften, 5 minutes. Add the wine and cook, stirring occasionally, until reduced by half, about 4 minutes. Return the turkey to the skillet, add the stock (plus a few pinches of salt to taste, depending on the salt content of your stock), bring to a boil, cover (with a lid or wrapped tightly with aluminum foil), and transfer to the oven. Cook until the meat is tender and falling off the bone, 2 hours.
Using tongs, remove the turkey pieces to a plate, then reduce the liquid on the stovetop over medium-high heat until thickened and gravy-like, 15-20 minutes (if you want it even thicker, towards the end mix a tablespoon of flour with ½ cup of the gravy then mix that back into the pan and simmer for 5 more minutes so it's fully incorporated). Return the turkey to the pan, cover with the gravy, season with more salt to taste (you know I’m obsessed with salt and need it in reach at all times), and enjoy!