In a medium bowl, sift and mix 2/3 cup (150 g) of flour with the starch and salt. Add the water and stir until you get a smooth mixture. Cover the mixture and let it rise for about an hour. Cut the fish fillet in diagonal pieces. Roll them in dill.
Heat the oil to 347°F (175 °C). Before frying, sprinkle the crumbing mixture with baking soda and mix it well. Add the remaining flour in a medium bowl. Add salt and white pepper. Roll the pieces of fish first in the flour, then in the crumbing mix.
Fry them for 2-3 minutes until crispy. Remove them from the heat and drain them from the oil on a napkin. Garnish them with lemon slices.