Q. Are you allowed to sell with the chometz an open large bag of flour, if you are machmir not to sell chometz gomur?
A. Poskim mention that there is room to be stringent in including in the sale of chometz to Gentiles chometz gomur or items that are certain to be chometz such as bread and many other baked good. The reason being that there are a number of leniencies involved in the process of the chometz sale and therefore when Biblically prohibited chometz is involved, we should abstain from having it included in that sale. (Maase Rav quoting Hagr’a, Igros Sofrim 48 quoting Rab. Akiva Eiger, Orchos Rabbenu – Pesach: 19 quoting of Chazon Ish, Teshuvos Vehanhogos 1: 309, and others).
However, in regards to dry flour that did not come in contact with water Poskim are lenient. (Teshuvos Vehanhogos – ibid., Orchos Rabbenu, ibid., Piskei Teshuvos 448: n. 44).
Horav Shlomo Miller’s Shlit’a opinion is that when needed one can be lenient.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a