Add raw cashews to a mixing bowl and cover with boiling hot water. Let rest for 1 hour (uncovered). Then drain thoroughly.
In the meantime, preheat oven to 350°F (180°C) and line a standard loaf pan (or 8x8 inch baking dish (adjust number/size of pan if altering batch size) with parchment paper. Set aside.
Add oats, almonds, sea salt, and coconut sugar to a high speed blender and mix on high until a fine meal is achieved.
Remove lid and add melted coconut oil, starting with 4 Tbsp and adding more if it's too dry. Pulse/mix on low until a loose dough is formed, scraping down sides as needed. You should be able to squeeze the mixture between two fingers and form a dough instead of it crumbling. If too dry, add a bit more melted coconut oil.
Transfer mixture to parchment-lined loaf pan and spread evenly to distribute. Then place parchment paper on top and use a flat-bottomed object, like a drinking glass, to press down firmly until it’s evenly distributed and well packed. Let it come up the sides a little, otherwise it can be too thick on the bottom.
Bake for 15 minutes, then increase heat to 375°F (190°C) and bake for 5-10 minutes more, or until the edges are golden brown and there is some browning on the surface. Remove from oven to cool slightly, then reduce oven heat to 325°F (160°C).
Once cashews are soaked and drained, add to a high speed blender with coconut cream, vegan cream cheese, arrowroot starch, vanilla, maple syrup, coconut oil, lemon zest, lemon juice, and sea salt. Blend on high until very creamy and smooth, scraping down sides as needed.
Taste and adjust flavor as needed, adding more lemon juice for acidity, lemon zest for tartness, salt for flavor balance, and maple syrup for sweetness.
Pour filling over the pre-baked crust and spread into an even layer. Tap on counter to remove air bubbles.
Bake for 50 minutes to 1 hour, until the edges look very slightly dry and the center appears only slightly “jiggly” but not liquidy. When you shake it, it will have some give to it, but it shouldn't all look liquid - only the center should jiggle.
Let rest for 10 minutes at room temperature, then transfer to refrigerator to let cool completely (uncovered). Once cooled, cover (waiting until cool will prevent condensation) and continue refrigerating for a total of 5-6 hours, preferably overnight.
To serve, lift out of pan with parchment paper and cut into bars or triangles. (I carefully cut off the very end pieces because they weren't as creamy as the center pieces.)
Enjoy as is or with coconut whipped cream and/or fresh berries. Store leftovers in the refrigerator, covered, up to 3-4 days, though best within the first 2 days.