Heat the oven to 350°F. Brush an 18-by-13-inch rimmed baking sheet with one tablespoon of the melted butter.
Combine the flour, baking powder, baking soda, and salt. Add the skyr. Add the water to the empty container and swish to clean and remove any lingering yogurt. Add milky water to the bowl. Add the eggs, honey, remaining 3 tablespoons melted butter, orange juice and zest, and vanilla. Stir to combine with a rubber spatula. (The batter will be thick.)
Spoon into the prepared sheet pan. Smooth the top with the spatula. Transfer to the oven and bake until golden brown and slightly dark at the edges, 20 to 22 minutes.
Once the Pancake Sheetcake has cooked, remove the pan from the oven and transfer it to a rack to cool slightly. Using a serrated knife, slice the pancake into 16 pieces. Transfer to a platter and garnish with pomegranate arils, clementines, and mint. Keep warm until ready to serve with maple syrup.