Preheat the oven to 425 degrees. Place sliced potatoes in a large plastic bag. Pour in ½ cupof olive oil, sea salt and black pepper. Toss in a bag until evenly coated, add more olive oil if desired, or until evenly coated. Spread potatoes flat on a cookie sheet without overlapping and bake in oven until golden brown around the edges. Bake 15-20 minutes and turn potatoes, baking another 15-20 minutes on opposite side. Bake longer if desired for crispness, but be sure not to burn. Serve with guacamole. For the guacamole, mash avocados to a chunky consistency. Gently mix in lemon juice, ume plum vinegar, ginger, yeast flakes and spices. Add tomato, onion and cilantro. Season to taste.