Grab a large mixing bowl, and combine flour, salt, and baking soda. Add the milk and butter and mix until it's a stiff dough. Flour the countertop, and punch the dough on the floured countertop, turning it over a few times. Roll out very thin and cut into squares. Prick with a fork. Bake at 400 degrees until the edges are lightly brown. I use a greased cookie sheet to bake mine.