Cut your 4-pound chuck roast into 4-inch cubes. Don't make them smaller—smaller pieces dry out faster during the long cooking. Pat them dry with paper towels before adding to the slow cooker. This removes surface moisture and helps the meat brown better if you sear it first (optional, but adds depth for zero extra cost). Add the beef cubes to your slow cooker along with 8 cups of water. The water should cover the beef by about two inches. Add ½ of your onion (leave the skin on—it adds color to the broth), all 8 garlic cloves, 1 tablespoon of kosher salt, ½ tablespoon of black peppercorns, 3 bay leaves, oregano, marjoram, mint, and thyme if using them. This is your beef broth foundation. Everything here will cook together for 8 to 10 hours on low. Don't use high heat—it toughens the meat and makes the broth cloudy. Low heat is what transforms tough into tender.

Set your slow cooker on low and let it run for 8 to 10 hours. The longer you cook, the more the collagen breaks down into gelatin. This creates a naturally rich, silky broth without any added stock or bones. At around hour 6, take a quick look to make sure the liquid hasn't evaporated below the beef level. If it has, add 1 to 2 cups of water. I usually start mine in the morning and let it go all day. By evening, the house smells extraordinary, and the hard work is done. This is how you make restaurant-quality food in your regular kitchen—you simply give it time.

After 8 to 10 hours, carefully remove the beef with a slotted spoon or tongs. Set it aside on a cutting board. Use a fine mesh strainer to strain all the broth into a large bowl or pot. Press gently on the solids to extract every bit of liquid. Discard the bay leaves, peppercorns, onion skins, and herb sprigs. These added flavor but aren't pleasant to eat. While the broth is still warm, shred the beef with two forks. Pull the meat apart into bite-sized pieces. Discard any large pieces of fat (some marbling is fine and adds flavor, but trim the obvious fat). Taste the shredded meat and season with additional salt if needed. Put the shredded meat back into the slow cooker with the strained broth. Keep the slow cooker on warm setting while you make the chile sauce.

While the meat cooks, prepare your chiles. Remove the stems and seeds from 8 guajillo chiles and 2 ancho chiles (if using). Don't rinse them yet. Cut them open lengthwise with kitchen scissors and shake out the seeds over a trash can. Some seeds will stick—use your fingers to remove what you can. Toast the cleaned chiles in a dry skillet over medium heat for about 2 minutes per side. You'll hear them crackle slightly and smell an amazing toasted-chile aroma. Don't burn them—they go from fragrant to bitter quickly. This toasting step is completely free but transforms the flavor from flat to deep. Place the toasted chiles in a bowl and pour hot water over them. Let them soak for 10 minutes until they're soft and pliable. This rehydrates them so they blend smoothly.

Drain the soaked chiles, reserving the soaking liquid. Add them to a blender along with 5 cups of your reserved beef broth, the remaining ¼ onion (rough chopped), 3 garlic cloves, 2 teaspoons of salt, and 1 cup of the chile soaking liquid. Blend on high until completely smooth. This takes 2 to 3 minutes. If your blender struggles, add more of the soaking liquid in small amounts. Strain this chile sauce through a fine mesh strainer into a bowl, pushing it through with the back of a spoon. This removes any tiny chile skin pieces and makes the sauce silky. Taste and adjust salt as needed.

Pour the smooth chile sauce into the slow cooker with the shredded beef and remaining broth. Stir gently to combine. The birria should look deep reddish-brown and smell incredible. Taste it again and adjust salt one final time. The broth should taste rich but not overly salty. Remember, you'll be adding acidic lime juice and fresh toppings, which change the flavor balance. Keep the birria on the warm setting until you're ready to serve. It holds beautifully for up to 2 hours. If you're making it ahead, cool it completely, divide it into containers, and refrigerate or freeze.