This might work with flour, but I don't believe it is going to work with corn starch. If you add a hot liquid to corn starch, it clumps immediately. We're talking a corn starch rock.Try tempering it, instead. Put some of the flour or cornstarch in a bowl, and add a bit (a cup, depending on how much you are actually working with) of the hot liquid, whisking till incorporated. Then, slowly add that to the simmering pot. This method should prevent clumping.
BUt the original question was about flour.
You had to look at the location of the questioner. In Europe, the terms are interchangeable, but in the U.S., particularly the southwest U.S., corn flour, or masa harina, which is made from dried corn which has been soaked in lime water, is used to make Mexican specialties such as corn tortillas, tamales, empanadas, etc. Corn starch, on the other hand, is a fine powdery substance made from the endosperm of the corn kernal, and used as a thickening agent. Don't see to many enchiladas or tamales in Ireland these days.Providing Andy's coment, I see how the question as about cornstarch. Little did I know that people call starch - flour, or is it other way around, I'm confused.