Pour the heavy cream, sugar, extract, and salt into a mason jar.
Cover and seal the lid tightly onto the jar.
Shake the jar for about four minutes.
Once the cream is thick and coats the back of a spoon, add whatever extra ingredients you like. Then, cover the mason jar again and shake one last time.
Cover and freeze for at least three hours.
Before serving, you can add toppings to the top of the ice cream.
Before serving, remove the ice cream from the freezer and allow it to soften for a couple of minutes before serving.