To make a snowman in Animal Crossing: New Horizons, you need to collect snowballs from the ground and stack them on top of each other to create the base of the snowman. Once you have the base, you can then use different materials to customize the snowman's appearance, such as a carrot for the nose, rocks for the eyes and mouth, and a hat to top it off. You can also use other decorations to make your snowman unique and festive, such as a scarf or other holiday items.