One and half teaspoon of arrow root powder, or a little more of flour, needs to be mixed in about two cups of water. Add the water, a little at a time, to the flour, so that the flour can be easily mixed. After the light mixture is ready, place it over heat and bring to boil. Keep constantly stirring till the mixture comes to a thicker consistency. Test it with a spoon, till the back of the spoon is coated. The consistency is just ready to be used, and the mixture will be by now reduced to about one cup of liquid. After cooling it, add it to about one liter of water. You have your starch ready for one or two dresses.
Just a word of caution: I have never measured the ingredients, as indicated in this recipe, but always used approximation. So please try and get your own perfected recipe.
Other than this, you may get starch by draining off water from a pan of boiled rice, if you add a little extra water to the rice when cooking it. After cooling this starch, strain it, and then use for starching clothes.