In a bowl, combine the gochujang, tomato sauce (ketchup) & sriracha sauce. Mix well.
In a separate bowl, combine the Chinese 5 spice powder, onion powder, garlic powder & sea salt flakes. Mix well.
Season the pork ribs on both sides with the Chinese 5 spice mix rubbing it in with your hands. Use a pastry brush to rub the gochujang mix over both sides of the pork ribs. Reserve ⅓ of the sauce for later in the recipe.
Place the rubbed & marinated pork ribs onto a sheet of baking paper & wrap tightly. Transfer the wrapped ribs onto a sheet of aluminium foil & wrap again (make sure there's no holes or the ribs are visible). Place onto a baking tray lined with parchment paper & bake in the preheated oven for 2 hours & 15 minutes.
Remove the ribs from the oven & increase the heat to 200°c-390°f.
Carefully unwrap the ribs (you can allow them to cool down for 15-20 minutes if you wish to do so) & place them onto a baking tray lined with clean parchment paper (you can use the same tray to save dishes). Brush over the remaining marinade & place it back into the oven for 7 minutes or until starting to char. Remove & serve.