Preheat oven to 325º and line two large baking sheets with parchment paper.
Make the oreo cookie dough. In a medium bowl, whisk together flour, cocoa powder, and sea salt until no clumps remain. In a large bowl, cream softened coconut oil and brown sugar with electric mixer. Whip until fully homogenized and slightly whippy. Beat in vanilla extract, then gradually add dry mix and beat on low until just combined. It will be a bit crumbly. Use your hands to bring the dough together and knead down into a ½" disk. Cover with plastic wrap and refrigerate.
Roll out dough on a dry surface lightly dusted with powdered sugar until dough is ¼-inch thick. Cut out 2 inch circles and transfer onto parchment paper with an offset (or other metaspatula, leaving 1 inch between cookies. Gather dough scraps, roll again, and cut again, this time cutting small ½-1 inch hearts, for garnish.
Bake circles and hearts separately. Circles bake about 20 minutes, or until the tops are no longer shiny. Hearts bake 5-10 minutes, depending on their size. Again, remove when tops are no longer shiny. Let cool completely, then store in the fridge until ready for use.