Let pizza dough stand at room temperature 15 minutes. Preheat oven to 450°F.

Heat a large skillet over medium-low. Add oil and garlic; cook, swirling occasionally, until garlic is golden, about 2 to 4 minutes. Drain oil from skillet into a small bowl to reserve, keeping garlic in skillet. Add spinach to skillet; increase heat to medium-high, and cook, tossing constantly, until spinach is wilted, about 2 minutes. Let stand 10 minutes to cool.

Stir together ricotta and Parmesan in a medium bowl. Add spinach mixture and chicken; stir well to combine.

Place dough on a large piece of parchment paper, and roll dough into a 20-x-6-inch rectangle. Spoon chicken mixture down center of dough to make an approximately 20-x 3-inch strip. Using a pizza cutter or sharp knife, create tabs in dough on both sides of filling:

Starting at the edge of dough, cut 1½-inch-long diagonal slits (½ inch to ¾ inch apart) in toward filling. Fold tabs over filling, and pinch tabs together to seal. Carefully shape stuffed dough into a ring; pinch ends of dough together to seal.

Transfer the stromboli ring on parchment to a baking sheet; fold or cut away excess parchment to fit baking sheet. Brush half of reserved garlic-infused oil over dough. Bake stromboli at 450°F until dough is browned, about 18 minutes. Remove from oven; brush with remaining garlic oil. Let stand 5 minutes before serving.