Cheat's sourdough

Name: Cheat's sourdough
Prep time: 20 min
Cook time: 74 h
Total time: 74 h 20 min
Cuisine: European, World Cuisine
Ingredients: 100 g plain flour; 75 g warm water; 1 pinch salt; ⅛ tsp dried instant yeast; olive oil spray; 50 - 70 g potato; 750 g water; 500 g baker's flour; 1 tbsp oil; 1 ½ tsp salt; ½ tsp dried instant yeast; warm water