In a large bowl, whisk the milk, sugar, and vanilla together until the sugar dissolves. Pour into the bowl of an ice cream maker.
Layer cubed ice and rock salt around the ice cream bowl. (More salt will help the ice cream freeze faster.)
Secure lid on top of the ice cream bowl. Process for 20-30 minutes or as instructed for your specific ice cream maker, adding more ice and salt as needed.
Enjoy immediately as soft serve ice cream, or place in a freezer safe container and freeze 2-3 hours for a stiffer ice cream.