Make the crust: In a food processor, place the dates, walnuts, oats, and salt and process until the mixture comes together into a sticky ball. If necessary, gradually add 1 to 2 tablespoons of water.
Line a 7 x 9-inch or 8 x 8-inch baking pan with parchment paper and press the crust to the edges of the pan. The crust is very sticky, so I like to use a sheet of parchment paper on top to help smooth it out. Place the pan in the freezer while you make the filling.
Make the filling: In a high-speed blender, puree the coconut cream, cashews, lemon zest, lemon juice, maple syrup, and salt until smooth. Pour the filling over the crust and freeze overnight. Let thaw at room temperature for 20 minutes before slicing into bars and serving.