Freeze guanciale for at least 15 minutes, and up to 45 minutes (partially freezing the guanciale makes it easier to slice).
Using a sharp chef's knife, cut into 1/4-inch-thick planks, then cut planks into 1/4-inch-thick batons (lardons).
In a large 12-inch stainless steel skillet, heat oil over medium-low heat until shimmering.
Add guanciale and cook, stirring occasionally, until the fat has rendered and guanciale is golden brown and crisp, about 15 minutes.
Using a slotted spoon, transfer guanciale to a plate; set aside.
Reduce heat to low, and bloom about 1 teaspoon freshly ground black pepper in rendered guanciale fat until pepper foams and is aromatic, about 1 minute. Remove skillet from heat.