Set oven rack to its uppermost position. Preheat oven to 475°F.
Drizzle room temperature pizza dough with 1 tbsp olive oil and press out to a 10" round. Cover loosely with plastic wrap.
Heat 1 tbsp olive oil in a 10" cast-iron skillet. Add Italian sausage and cook over medium, breaking up any large pieces. Once cooked and slightly crisp remove to a paper towel-lined plate.
With the heat still on medium/low, immediately lay pizza dough in the pan, stretching out to the edges using a spatula or spoon if necessary. Top dough with marinara, then mozzarella, fennel, garlic and sausage. Drizzle with 1 tbsp olive oil and check the underside which should be starting to brown and crisp. Transfer pan to oven and bake until bubbling, about 10-14 minutes.
Remove from oven and allow to cool for 5 minutes, then sprinkle with red pepper flakes, and fennel fronds or fresh basil. Lift out of the pan and cut into wedges and serve.