In a mixing bowl, pour the heavy whipping cream, vanilla, sugar, and salt and mix well.
Pour the ice cream mixture into the small coffee can and secure the lid tightly.
Place the small coffee can into the center of the large coffee can.
Surround the small coffee can with about one inch of ice, then sprinkle a heavy heaping of rock salt on top.
Add another layer of ice and then salt. Continue until the salt and ice reach the very top of the coffee can.
Secure the lid on the extra large coffee can.
Roll and shake the coffee cans back and forth. Vigorous rolling is needed for 15-30 minutes.
As you roll it, the ice will melt. Add more salt and more ice, draining some of the water as needed.
When you check on your ice cream to see if it’s frozen, ensure that you don’t let the salty ice water drip into your ingredients or your ice cream will taste salty.
When the ice cream is frozen or has the consistency of soft serve, transfer the ice cream to a bowl or container and let it harden further in the freezer.