Season the chuck roast generously with salt and black pepper. Place the roast into your slow cooker, then pour in low-sodium beef broth and salsa, followed by ground cumin, chili powder, onion powder, garlic powder, and dried oregano. Cover and cook on LOW for 8 hours, until the beef is fork-tender and easily shreds.

Once the beef has finished cooking, carefully remove it from the slow cooker and let it cool slightly. Use two forks to shred the beef into bite-sized pieces, ensuring it's well-separated. Return the shredded beef to the sauce in the slow cooker, stirring to combine and soak in the flavors for about 10 minutes.

Transfer the sauce from the slow cooker into a medium saucepan and bring it to a gentle simmer over medium heat. While it heats, mix cornstarch and water to create a slurry. Gradually stir the slurry into the simmering sauce, cooking for about 5 minutes or until it thickens.

Preheat your oven to 350°F (175°C). On a clean surface, take your flour or corn tortillas and fill each with a generous amount of the shredded beef mixture and a sprinkle of shredded cheese. Roll them up tightly and place them seam-side down in a greased baking dish.

Pour a desired amount of the thickened sauce over the top of the enchiladas, ensuring each is generously covered. Finish by sprinkling any remaining shredded cheddar and Monterey Jack cheese over the sauced enchiladas.

Carefully place the baking dish in your preheated oven and bake for 30 minutes, or until the cheese is bubbly and golden brown.

Remove them from the oven and let them sit for a few minutes. Serve warm, garnished with fresh pico de gallo, a dollop of sour cream, or slices of avocado.