On a 6-quart Instant Pot, select More/High Sauté. Add 1 tablespoon of oil and the pancetta. Cook, stirring occasionally, until well-browned and crisp, 5 to 6 minutes. Using a slotted spoon, transfer to a paper towel–lined plate; set aside. Add the garlic and pepper flakes, then cook, stirring, until fragrant, 30 to 60 seconds. Pour in the wine and cook until most of the liquid has evaporated, 7 to 9 minutes. Add the tomatoes and cook, stirring occasionally, until they begin to stick to the pot, about 8 minutes. Add the reserved tomato juices and 4 cups water; stir to combine, then distribute the mixture in an even layer. Add the pasta, placing the strands horizontally so they lay flat, then press them into the liquid until submerged. Set the pecorino chunk on top.