Cut off the thick parsley stems. I also remove thinner stems to improve the texture of the chimichurri.
Finely chop the parsley with a knife (if making large quantities you can use a food processor but don't overblend it
In a bowl or jar, combine the olive oil, red wine vinegar, garlic, oregano, red pepper flakes, and salt.
Stir in the parsley and give it a good stir. Let it sit for 15 minutes before serving or store it in the refrigerator for up to 5 days.
Notes
Note that high-quality extra-virgin olive oil will solidify in the fridge. You may have to take your chimichurri out 10-15 minutes before serving to allow the oil to come to room temperature.
Chimichurri freezes really well for up to 3 months. My tip is to freeze the chimichurri in an ice cube tray. The small size of the cubes makes them thaw quicker.