Season the roast with salt and pepper on all sides, then place it in the bottom of your slow cooker.
Whisk together beef broth, salsa, cumin, chili powder, oregano, onion powder, and garlic powder. Pour the mixture over the roast.
Cover and cook on LOW for 8 hours or until the beef is tender and shreds easily. Remove the roast to a large plate and shred it.
Transfer the sauce from the slow cooker into a saucepan over medium heat. Slowly whisk in the cornstarch slurry. Cook for a few minutes until the sauce begins to thicken. Taste and adjust seasoning, adding more salt and pepper or other seasonings if needed.
Preheat the oven to 350 degrees F.
Toss the shredded beef with ½ cup of the sauce. Fill each tortilla with a spoonful of shredded beef and shredded cheese, then roll them up and place them in a baking pan seam-side down.
Pour the desired amount of sauce over the enchiladas and top with the remaining cheese.
Bake for 30 minutes or until bubbly.