1) In a medium saucepan over medium-high heat, combine salt and water and stir to combine and dissolve salt. Remove brine from heat and let cool to room temperature. Cut 1cm slits between bones on underside of rib racks. Place ribs in a large resealable bag set in a baking dish. Pour in the salt brine, seal the bag and refrigerate for at least 5 hours, or overnight.
2) Preheat oven to 135C/Gas 1. In a small saucepan, add the vinegar, sugar, hot sauce, red chilli flakes, 2 teaspoons liquid smoke, Worcestershire sauce and salt and pepper, to taste. Bring to the boil over medium heat. Whisk until well combined, then remove from heat. Reserve 250ml of mixture as dipping sauce and hold, covered, in the refrigerator until ready to serve. Reserve remaining mixture to baste the ribs as they cook.
3) Remove ribs from the refrigerator and discard brine. Pat ribs dry and transfer to a rimmed baking tray lined with a wire rack. Combine beer with 1 tablespoon liquid smoke in a small bowl and pour into the bottom of the baking sheet. Brush pork with marinade on both sides. Bake in the preheated oven, brushing every 20 minutes or so. Cook for about 3 hours or until the meat is knife-tender.
Remove ribs from the oven to a serving platter and serve with reserved dipping sauce.