Maruska's Horseradish Coleslaw

1 green medium size cabbage, thinly sliced
1 horseradish root, peeled and shredded 
3 carrots, peeled and shredded 
1 onion, diced
1 - 2 teaspoons Celtic sea salt 
1/4 cup olive oil
1/4 teaspoon mustard seeds (optional) 
1/4 cup rice vinegar 

- Mix all the ingredients in a large bowl. Store in mason jars in the fridge for 24 hours to marinade before eating.