Preheat oven to 350°. Spray an 8-inch square baking pan lightly with baking spray; line on all sides of pan with parchment paper, letting excess extend over sides.
In the work bowl of a food processor, combine 1 cup pistachios, oats, ¼ cup coconut flakes, orange zest, and salt. Pulse until coarse, 10 to 12 times.
In a small bowl, whisk together honey and olive oil. Add honey mixture to pistachio mixture and pulse until well combined and mixture holds when pressed together.
Transfer mixture to prepared pan, spreading evenly. Top with remaining ¼ cup pistachios and remaining ¼ cup coconut flakes and gently press into top to adhere.
Bake until golden brown, 12 to 15 minutes. Let cool completely in pan. Using excess parchment as handles, lift and transfer to cutting board; cut into squares. Garnish with flaky sea salt, if desired. Stored at room temperature in an airtight container for up to 3 days.
Recipe by Victoria at https://victoriamag.com/orange-pistachio-oat-squares/