"I had never made prime rib before, but this slow-roasted recipe is so easy. It originated from my mother-in-law who makes prime rib often; with a lot of research, I have made a few changes and prefer my recipe with the alterations."
Mix liquid seasoning and Worcestershire sauce together with garlic in a bowl. Pour over prime rib in a container. Marinate, turning every 30 minutes, 1 to 2 hours.
Preheat the oven to 450 degrees F (230 degrees C).
Place prime rib on a baking rack set inside a large baking dish.
Bake in the preheated oven until all juices are sealed in, about 45 minutes. Reduce temperature to 325 degrees F (165 degrees C) and continue roasting until an instant-read thermometer inserted into the center reads 130 to 140 degrees F (54 to 60 degrees C), about 2 hours more. Let sit 30 minutes to 1 hour before slicing.