Place a pizza stone or inverted baking sheet in the oven. Preheat to 475°F for at least 30 minutes.

Cut off the dark green portion and root end. Split the white and light-green portion lengthwise, rinse thoroughly, and slice thinly.

Fry the chopped bacon in a skillet over medium heat until crisp, about 6–8 minutes. Transfer it to a paper towel-lined plate. Leave about 1 tablespoon bacon fat in the skillet.

Add the sliced leek to the skillet and cook over medium-low heat until soft, about 5 minutes. Stir in the garlic and thyme; cook for 30 seconds. Remove from the heat.

Slice the potato into very thin rounds, about ⅛ inch thick. Place in a microwave-safe bowl with 1 tablespoon water, cover loosely, and microwave for 2–3 minutes, just until slightly tender. Drain and pat dry. Toss with the olive oil, ¼ teaspoon salt, and pepper.

Sprinkle cornmeal or flour over a sheet of parchment paper. Stretch or roll the dough into a roughly 14-inch circle.

Brush the dough lightly with olive oil. Sprinkle on the mozzarella, leaving a ½-inch border. Distribute the cooked leek, potato slices, bacon, and goat cheese evenly over the top. Season with the remaining ¼ teaspoon salt.

Slide the pizza, still on the parchment, onto the hot stone or baking sheet. Bake for 12–16 minutes, until the crust is golden and the potatoes are tender. For extra browning, broil for 1 minute at the end, watching carefully.

Let rest for 3–5 minutes, then slice. Garnish with red pepper flakes or fresh arugula if desired.