Place dates in a medium bowl and fill with boiling water, making sure dates are fully submerged in water. Soak dates for 10-15 minutes, until soft.
Line a large loaf pan (9 x 5 or 10 x 5) with unbleached parchment paper.
In a food processor or blender, blend dates with 1 Tablespoon of soaking liquid, nut butter, coconut oil, salt and vanilla until smooth. Transfer mixture to a large bowl and stir in oats, shredded coconut, nuts and seeds. Stir until well combined. If you have a large capacity food processor, remove the blade and stir in rolled oats, coconut, nuts and seeds into the food processor bowl. Mix until well combined.
Transfer mixture to prepared loaf pan and spread evenly in one layer and smooth at the top.
Melt chocolate and coconut oil in a heat-proof bowl set over a pot of simmering water.
Spread melted chocolate evenly over oat mixture. Sprinkle with flaky sea salt and refrigerate until mixture is firm, about 8 hours to overnight. (chocolate will be firm, but filling will be sticky and medium firm). The longer they stay in the fridge, the firmer they will get.
Remove mixture from the loaf pan and cut into bars or squares. Store leftovers in the refrigerator.