Trim excess fat from the brisket, pot roast, or shoulder roast.

Season the meat with salt and pepper.

Place the meat in a 13 x 9 x 2-inch baking pan.

Cover the meat with sliced onions.

Sprinkle the onions lightly with salt.

Reserve 1/3 cup of beer.

Combine the remaining beer with brown sugar, instant beef bouillon granules, black peppercorns, minced garlic, bay leaf, and dried thyme.

Pour the beer mixture over the meat.

Cover the baking pan tightly with foil.

Bake in a preheated 350°F (175°C) oven for 3 to 3 1/2 hours, or until the meat is very tender.

Remove the meat from the pan and transfer it to a serving platter.

Keep the meat warm.

Skim off any excess fat from the pan juices.

Remove the bay leaf from the pan juices.

Transfer the pan juices to a saucepan.

Cook the juices over medium heat until they reduce to approximately 2 cups.

In a small bowl, combine the reserved beer and all-purpose flour, stirring until smooth to create a slurry.

Gradually whisk the beer-flour slurry into the simmering pan juices.

Continue to cook and stir the gravy until it thickens and begins to bubble.

Cook and stir for an additional 1 to 2 minutes to ensure the flour is cooked through and the gravy is smooth.

Serve the beef carbonade with the gravy spooned over the meat, or serve the gravy separately.