Carefully inspect the neck bones and remove any loose bone fragments. Do not rinse the raw pork. Pat the neck bones completely dry with paper towels.
Combine the kosher salt, garlic powder, onion powder, smoked paprika, black pepper, dried thyme, and optional cayenne pepper. Season the neck bones evenly on all sides.
Heat the oil in a large Dutch oven or heavy-bottomed pot over medium-high heat.
Working in batches, brown the neck bones for 3–4 minutes per side. Avoid overcrowding the pot. Transfer each browned batch to a plate.
Reduce the heat to medium. Add the diced onion to the same pot and cook for 5–7 minutes, stirring occasionally, until softened and lightly browned.
Add the minced garlic and cook for 30 seconds.
Sprinkle the flour over the onions. Cook for 2 minutes, stirring constantly, until the flour is fully incorporated and lightly browned.
Slowly pour in the broth while stirring and scraping the browned bits from the bottom of the pot.
Stir in the Worcestershire sauce and optional browning sauce. Add the bay leaf.
Return the neck bones and any collected juices to the pot. The liquid should come approximately three-quarters of the way up the pork. Add a little more broth if necessary.
Bring the liquid to a gentle simmer. Cover the pot, reduce the heat to low, and cook for 2½–3 hours. Turn the neck bones occasionally and check the liquid level as they cook.
Once the meat is fork-tender and easily pulls away from the bones, transfer the neck bones to a serving dish. Discard the bay leaf.
Simmer the gravy uncovered for 5–10 minutes, stirring occasionally, until it reaches your preferred consistency.
Taste the gravy and adjust the salt and pepper as needed. Return the neck bones to the pot and spoon the gravy over them.
Remove the pot from the heat and let the neck bones rest in the gravy for 10 minutes.
Garnish with chopped parsley and serve over hot white rice with cabbage or green beans.