How to Make It
Place a pizza stone on middle oven rack. Preheat oven to 500°F. Stir together flour, 1/2 cup plus 2 tablespoons water, oil, and 1/2 teaspoon salt in a large bowl until well combined and a dough forms. Lightly coat a second large bowl with oil. Transfer dough to oiled bowl; cover and let stand 15 minutes.
Turn dough out onto a lightly floured work surface; divide into 8 pieces. Roll each piece into an 11- x 8-inch rectangle. Gently poke holes all over rolled dough using a fork. Brush dough rectangles lightly with oil, and sprinkle evenly with remaining 1/2 teaspoon salt.
Working in batches, transfer dough rectangles to hot pizza stone. Bake in preheated oven until bubbly and golden brown in spots, about 4 minutes. Transfer to a wire rack; let cool completely, about 10 minutes. Serve with horseradish butter. Store matzo in a ziplock plastic bag at room temperature up to 3 days.