In your mason jar, layer feta, olives and spices. This ensures the jar has spices mixed throughout.
At the second layer, place oregano sprigs into the sides of the jar for garnish.
Once the jar is full, pour the olive oil to top off the jar.
Marinate in the refrigerator for at least 8 hours for the best flavor. Allow to come to room temperature before using. Use leftover oil for dipping, sauce, dressing, etc!