Preheat oven to 475. Brush bottom of a 16 by 11 inch rimmed baking sheet with 1 tablespoons olive oil. Press and stretch dough evenly to cover bottom of sheet. ( If dough resists at first, let it rest for a minute before continuing.).
Toss potatoes with 1 tablespoons olive oil and scatter over dough. Sprinkle with salt. Scatter spinach over potatoes. Sprinkle with cheese.
Bake until underside of crust is golden ( lift an edge of pizza with a spatula to peek.) and cheese is bubbling, about 20 minutes. Let stand 5 minutes on a wire rack before slicing.
Tips: If Gruyere is too strong for your taste, substitute Jack cheese. Or give the pizza a Greek flair with crumbled feta. Sprinkle on chopped sun dried tomatoes and oregano, too.