Hi – what can I replace the 1/2 cup of …

Name: Gluten-Free Sourdough Rolls
Prep time: PT-479654H18M8S
Cook time: PT-479654H18M8S
Total time: PT-479654H18M8S
Cuisine: Plant-Based
Ingredients: 1 cup light buckwheat flour (120g); 1/2 cup white rice flour (70g); 1/2 cup brown rice flour (65g); 1/2 cup tapioca flour/starch (60g); 1/2 cup potato starch (70g); 1/2 cup seed or nut flour (50g); 3 tablespoons whole psyllium husk (21g); 1 tablespoon coconut palm sugar (8g); 1/2 tablespoon sea salt (6g); 1/2 cup active GF sourdough starter (132g); 1 cup homemade hemp milk (240g); 1 cup warm water (240g); Olive oil (optional)