The Shulhan Aruch (Orah Haim 206:4) says that whenever one is reciting a blessing over a food or a fragrance, one should hold it in one’s right hand. The Mishna Berura (O.H. 206:18) explains that the right hand is considered more important and as such it is fitting for to use it for blessings. The Mishna Berura quotes an opinion from and rules like Rabbi Akiva Eiger, who says that with regards to a leftie, one’s left hand is more dominant and therefore one would use that hand for the blessing. Nevertheless, the Kaf HaHaim says that even in such a case, a leftie should still use the right hand because according to Kabbalah, the right hand represents the attribute of Hesed (kindness) and is preferable over the left hand.
The Mishna Berura goes on to say that when one is given a Sefer (in this context, Sefer refers to a book of Hebrew religious literature), one should accept it with one’s right hand. Rabbi Haim Kanievsky says that just as with reciting blessings, one should accept a Sefer with one’s dominant hand, but when it comes to taking a Torah scroll, one should always use one’s right hand.
Another related Halacha is that one should hold whatever one is reciting a blessing over. The Mishna Berura (O.H. 206:17) says that one reason is that by holding it, one has proper intent while reciting the blessing. Elsewhere in the Shulhan Aruch, the Mishna Berura (O.H. 167:22) says that another reason is that by holding the food or fragrance, one minimizes the possibility of a disruption between the blessing and the consumption of whatever one is holding. If one recites a blessing while the object was not in one’s hand but rather is laid down on a table or other surface, the blessing is still valid, Bediavad (ex post facto).
Although there is no clear Moroccan custom, most Sephardic authorities, including the Kaf HaHaim and the Sde Hemed say that one should use one’s right hand while reciting a blessing, regardless of one’s dexterity.
Summary: While reciting a blessing one should hold the food, drink or fragrance with one;s right hand, even if one is a leftie. One should hold a Torah scroll in one’s right arm.