In a large pot or container, heat 8 liters of water to 158°F/70°C with a sous vide machine.
Trim off any sinew and fat on the short ribs.
In a small bowl, combine the salt, brown sugar, pepper and garlic powder. Cover the ribs with the seasoning mix.
Pack the ribs into a sous vide bag and submerge in the water bath. Cook for 12 hours.
Remove the ribs from the bag, discard the bag and the remaining liquids. Cool the meat completely.
Preheat the oven to 410°F/210°C. Line a baking sheet with aluminum foil or parchment paper.
Place the ribs on the prepared baking sheet and pat them dry with a dish towel. Coat the ribs all over with the BBQ sauce, being generous with the sauce. Roast, uncovered, for 10-15 minutes, until the sauce starts to boil and stick to the ribs.
Finish with salt and pepper and serve.