Add the half and half, sugar and vanilla extract to a quart-size ziploc bag. Squeeze the excess air out of the bag before sealing it tight. Use your hands to squeeze the bag to mix the ingredients together.
Fill the gallon ziploc bag about half way up with ice and sprinkle it with salt. Place the quart ziploc bag over the ice, then seal up the gallon bag.
Shake the bag continuously, until the half and half mixture freezes and turns into ice cream! This could take about 5 minutes or more. Pro tip: use gloves to keep your hands warm!
Remove the bag of ice cream and quickly rinse it off to get any salt off of the bag. You don’t want salty ice cream! Then, open the bag and enjoy!