In a food processor, combine the soaked cashews, pitted dates, and shredded coconut. Pulse until the mixture is well combined and resembles a sticky dough.
Add the melted coconut oil, vanilla extract, and a pinch of salt to the mixture. Process again until smooth and creamy.
Line an 8x8-inch baking dish with parchment paper, leaving some overhang for easy removal.
Press the cashew mixture evenly into the bottom of the prepared baking dish. Use a spatula or your hands to ensure it's compact and level.
In a separate bowl, mash the blackberries with a fork until slightly chunky. Spread the mashed blackberries evenly over the cashew layer.
Place the dish in the refrigerator for at least 2 hours to set.
Once set, lift the slice out of the dish using the parchment paper overhang. Cut into squares or bars.