Trim any fat that is thick and hard, keep the squishy fat attached to provide moisture. Place 2 large and long sheets of foil on a flat surface, creating a "plus" sign.
Mix together brown sugar, salt, onion powder, garlic powder, paprika, black pepper, mustard and thyme. Spread half of the mixture on one side of the brisket and place the covered side down in the center of the foil. With remaining dry rub, spread on the top side of the brisket.
Wrap tightly in foil, overlapping and securing. Place on a baking sheet in the refrigerator overnight.
Remove from fridge 1 hour before cooking, letting it come to room temperature. Place a wire rack on a baking sheet and place wrapped brisket on top of the wire rack. Preheat oven to 275 and place a meat thermometer into the thickest part.
Bake for about 7-8 hours or until the temperature reaches 175 degrees F. When this temperature is reached, carefully rip the foil off the top (can brush bbq sauce on now if you like) and return to oven and continue to cook about one hour longer, until internal temperature reaches 195–205°F (or 90–96 degrees C.) to reach fall apart texture
Remove from oven and add a tent of foil to the top. Let brisket stand for 30-60 minutes allowing liquid to soak back into the meat. Not all liquid will return to the meat but most of it will. Slice against the grain and serve as desired.