Remove the steamed glutinous rice from the steamer and cool to room temperature. Turn occasionally with chopsticks to speed up cooling. Sprinkle a little cold water on the cooled glutinous rice and break it up with your hands. Use as little water as possible. Sprinkle the koji on the glutinous rice and stir while spreading, try to mix evenly. Don't be impatient, just spread a layer, mix well and then spread. Leave a little koji behind.
Transfer the glutinous rice to a fermentation container. A larger rice cooker will be fine. It is also used to soak glutinous rice. While placing, press lightly with the palm of your hand. After it's done, sprinkle the last bit of koji on top. Rinse the glutinous rice on your hands with a little cold water into the container, then press the glutinous rice with your hands and wipe it on the surface to make the surface smooth.
Finally, cover the glutinous rice with plastic wrap, leaving as little space as possible. Close the lid. Place in a warm place, such as a clothes basket.
I put the container in the oven. Old-fashioned ovens always have a little flame in them, just enough to maintain a mild temperature. This is a lazy way. It is best to use clothes or quilts to keep warm, as the indoor temperature is unstable in winter.
It'll be fine in about three days. Check at any time to see if there is any fever. Fever is a good sign. You can try it on the third day. The fermented glutinous rice is crisp, juicy, fragrant, sweet, not overpowering with wine, and cannot taste raw rice grains. At this time, you can remove the plastic wrap and the rice wine is ready. When done well, the glutinous rice will not fall apart and can be broken into pieces.