Jalapeño slices can go on the pizza either before or after it goes into the oven, depending on your preference for the level of spiciness and texture you desire.
Pre-oven: Placing jalapeño slices on the pizza before baking allows them to cook slightly in the oven. This method can mellow out their spiciness, making them a bit less intense. The heat from the oven will also soften the jalapeño slices, making them more tender.
Post-oven: If you prefer a fresh and fiery kick to your pizza, you can add the jalapeño slices after the pizza comes out of the oven. This way, the jalapeños will retain their crispiness and full spiciness.
Ultimately, the decision of when to add the jalapeño slices depends on your taste preference. If you're unsure, you can try both methods and see which one you prefer. Some people even like to do a combination, adding some jalapeños before baking and some after for a mix of flavors and textures. Enjoy your spicy pizza!