Mix the flax seeds with 15 tablespoons of warm tap water. Stir the mixture and set aside.
In the meantime, wash and peel the potatoes and carrots.
Grate them together with the zucchini very finely with a vegetable grater. Add a teaspoon of salt and mix with your hands. Put the mix aside - about 5 minutes.
Squeeze out the excess liquid with your hands. Put the vegetable mix in a kitchen towel and squeeze out the remaining liquid.
Now add cornstarch, mustard and the ground flax seeds. Knead all the ingredients together.
Season with salt and pepper.
Heat a frying pan and form patties. Fry the zucchini potato patties on both sides over medium heat with a little oil for about 5 minutes.