These two items are staples of the Sichuan pantry.
Sichuan hot oil
2 cups cooking oil [a]
1 cup coarsely ground dried red chiles, with seeds [bb]
Place the chiles in a saucepan off the heat. Heat the oil separately to 285 degrees F (140 degrees Celsius). Test the heat by pouring a small amount of oil onto the chiles. They should fizz gently but energetically and release a nice aroma. If the temperature is right, pour the rest of the oil over the chiles, stirring constantly. The oil should take on a deep ruby-red color and a wonderful aroma. If the oil is not hot enough and you're not getting the aroma, put the pan over heat. If the oil is too hot, add some cool oil. Make sure you don't burn the chiles. Allow the mixture to cool, then pour it (flakes and all) into a jar for storage.
ground roasted Sichuan peppercorns
Heat a dry wok or fry pan over low heat. Add 2 TBS whole Sichuan peppercorns [c] and stir for a few minutes, until the fragrance comes up. Be sure not to burn them. Allow them to cool down, then grind them to a fine powder in a mortar and pestle or a spice grinder.
NOTES
[a] Any neutral oil with a high smoke point will do. Avoid olive oil and other highly flavored oils. Peanut oil is my preference.
[bb] Any moderately hot chile will do. Freshness is important. Penzeys tien tsin chiles work well. My favorite here is the Fragrant Hot Ground Chilies from The Mala Market.
[c] The Sichuan peppercorns sold in Asian markets in the USA are almost always stale. The Mala Market imports them directly from Sichuan. The difference between stale and fresh Sichuan peppercorns is like night and day.