Melt coconut oil in a saucepan over medium-low heat or in the microwave for about 30 seconds. Stir cocoa powder, maple syrup or honey, and if using, vanilla extract and salt, into the melted coconut oil until completely smooth.
Pour mixture into a lined baking pan or sheet (I used a small sheet pan). Refrigerate until chilled, about 1 hour. Chop into chunks or bars. Store at cool room temperature or in the refrigerator.