In a large bowl, combine the beef, onion, garlic, parsley, dill, dried mint, egg and flour. Season with salt. Mix with your hands until well combined.
Roll 2 tablespoons of the beef mixture into a meatball, repeat to make 14 keftedes.
Heat ½ cup olive oil in a large frying pan over medium heat, add the keftedes and shallow-fry, turning occasionally, for 10 minutes or until golden brown.
For the avocado tzatziki, combine the ingredients in a bowl and season with salt and cracked pepper. Set aside until needed.
Preheat the oven to 180°C. Place potatoes onto a baking tray with lemon juice and remaining olive oil and roast for 35 minutes or until golden brown and crispy.
To serve, place the meatballs on a serving platter, serve with the avocado tzatziki and roasted lemon potatoes.
4 servings