Started a batch of natto this evening. 600g of dry soybeans soaked about 8 hours, then pressure cooked for 20 minutes. Mixed in some spores, put a thin layer of the beans in these glass containers, then covered with a damp cloth and lids. I'll keep these in my makeshift incubator (a cooler with a reptile cage heating mat) overnight at 40C, then put them in the fridge in the morning, and enjoy them the day after.
My natto comes out much like yours, a bit thin on the strings but tasty. I can’t get dry soy beans where I am so use chick peas or black eye beans.