Preheat the oven to 350°F. Put hazelnuts on a roasting pan and bake until they smell nutty and the skins crack, about 10-15 minutes. Remove, place in a clean dish towel and rub to remove some of the skins.
Put the hazelnuts into a jar and cover with water. Soak for at least 2 hours or overnight. Strain the hazelnuts. Rinse and put into a blender with 2 cups of fresh water. Blend until smooth and creamy. Strain through a cheesecloth until most of the liquid is removed.
Pour the nut milk into a bowl and add the maple syrup and salt to taste. Transfer to an ice cream maker or large baking dish and freeze. Temper slightly at room temperature before serving.