Preheat the oven to 350˚ F . Whisk the flour, baking powder and kosher salt in a medium bowl; set aside. In a large bowl, whisk the coconut oil and sugar. Whisk in the eggs, one at a time, and then the vanilla. Stir the dry ingredients into the wet ingredients and then fold in the sprinkles.
Line a baking sheet with parchment paper. Divide the dough in half, then form each half into a long rectangle, about 4 inches wide, on the baking sheet. Leave a good few inches in between the rectangles because they will spread in the oven. Sprinkle the tops with more sprinkles and a few pinches of sea salt and bake for 25 minutes.
Remove from the oven and reduce the oven temperature to 250˚ F. Transfer the rectangles to a cutting board and use a serrated knife to cut them into 1-inch-thick pieces. Place them on their sides on the baking sheet. Return to the oven and bake for 20 more minutes, or until desired crispiness. Transfer to a rack and let cool on the baking sheet.