For the base:
Heat oven to 350° and arrange a rack in the middle. Coat a 13-by-9-inch baking dish with coconut oil and line the pan with 2 pieces of parchment that overhang each side of the pan by 1 inch. In a food processor, finely grind pistachios with graham-cracker crumbs and salt until it resembles a fine meal. Add honey and coconut oil and process until mixture is thoroughly moistened and it begins to lump together, about 30 seconds. Press mixture into bottom of prepared pan. Bake until lightly browned, 10 to 12 minutes. Remove from the oven and let cool while you make the filling.
For the filling:
Place strawberries in the food processor and process until they?re a super smooth puree. Pass strawberry puree through a fine mesh sieve and press on the sieve with a spatula to extract as much of the puree as possible; discard any seeds. Combine puree with all ingredients in a large non-reactive bowl and whisk until sugar is dissolved and mixture is smooth, about 2 minutes. Pour filling over baked crust and return to the oven, and bake until just set in the middle, about 25 to 30 minutes. Remove from the oven and let cool completely on a wire rack, about 1 hour. Cover and place in refrigerator to set up for 2 to 3 hours. Using a knife dipped in hot water, cut into squares then, as desired, top with powdered sugar or toasted coconut flakes and serve.