Pour 1/2 cup of the almond milk in a liquid measuring cup and stir in tapioca starch until dissolved. Add remaining 1/2 cup almond milk and pour into a blender. Add coconut milk, lemon juice, maple syrup, lemon zest, vanilla extract, and sea salt. Blend until all ingredients are well combined. Pour into a bowl and place in freezer to chill for 20 minutes.

While ice cream mixture is chilling, prepare the crust. Grease a 9-inch pie or tart dish with coconut oil. Combine walnuts and coconut in a food processor and pulse until walnut are finely chopped. Add maple syrup and sea salt, and pulse again until walnut mixture is moistened, and nuts are very finely chopped. Spread walnut coconut mixture on the bottom of the pie/tart dish and set aside.

Remove the ice cream mixture from the freezer and pour into a chilled ice cream maker, and mix per manufacturers instructions {it took ~15 minutes for the ice cream to form in my Cuisinart Ice Cream Maker}. When it's ready, spread ice cream over crust and place in freezer for ~30 minutes, or until ice cream is firm,

Remove from freezer, top with blueberries, slice, and serve immediately.