In the work bowl of a food processor, combine the parsley, oregano, garlic, vinegar, salt, and chili flakes. Pulse 4-5 times to help start the blending process. Then, with the motor running, stream in the olive oil.
Taste and adjust acid, salt, and heat levels as you feel is needed.
When you're happy with it, scrap the chimichurri into a jar and refrigerate. It will keep at least a week in the fridge.