Spicy salmon mixed grain sushi

Name: Spicy salmon mixed-grain sushi
Ingredients: 1/2 cup (100g) brown rice; 1/4 cup (50g) tri-colour quinoa; 1/4 cup (50g) pearl barley; 2 cup (500ml) water; 1/4 cup (60ml) rice vinegar; 2 tablespoon caster (superfine) sugar; 1/2 teaspoon sea salt flakes; 1/4 cup (35g) sunflower seeds, chopped finely; 2 sheets toasted seaweed (nori); 200 gram sashimi-grade salmon, sliced thinly; 1/2 teaspoon chilli powder; 1 medium avocado (250g), sliced thinly; 1 teaspoon lemon juice; 2 lebanese cucumbers (260g), peeled, sliced thinly; 2 tablespoon rice vinegar; 1 tablespoon caster (superfine) sugar; 1 clove garlic, sliced thinly