Season the neck roast all over with kosher salt and black pepper. Heat a large cast iron skillet over medium-high heat. Add the oil and sear the neck until it is brown all over.
Slow Cook
Combine seared neck roast and all remaining ingredients in the slow cooker. Toss gently to combine. Cover and cook on low for 8 to 10 hours, or on high for 5 to 6 hours, or until the meat is tender and falls apart easily when shredded with a fork.
Serve
Use a pair of tongs or a slotted spoon to serve the venison barbacoa on tacos, or with a side of rice and beans.