Place red pepper flakes in a large measuring cup; set aside. In a mason jar, add dried chili peppers, granulated sugar and sea salt; set aside.
In a small saucepan over medium-high heat, combine grapeseed oil and sichuan peppercorns. Heat up the oil mixture until a slight smoke comes up, around 350ºF.
Remove from the heat and carefully pour in the measuring cup (the mixture will sizzle). Discard the peppercorns, stir and let it cool off before pouring it in the mason jar (these jars can handle around 205-207ºF). After pouring the oil in the prepared jar peppers, stir again and cool it down. Add some sesame oil and cover. Yield 1 ¼ cups.