1. Preheat oven to 475ºF. Brush bottom of a 16-by-11-inch rimmed baking sheet with olive oil. Gently press and stretch dough evenly to cover bottom of pan. (If dough resists at first, let it rest at room temperature for a few minutes and then continue.) Scatter pineapple and ham on top of dough, leaving a 1-inch border around edges. Sprinkle with cheese.
2. Bake until underside of dough is golden and cheese is bubbling, about 15 minutes. Sprinkle with scallions. Let stand 5 minutes on a wire rack before slicing and serving.