In a big bowl start by mix all the dry ingredients, then add the mashed potatoes, cooking oil and water, and with your hands start kneading the dough.
Knead for about 5min. The dough will become stretchy and shouldn't be too sticky. If it is too sticky add a bit more flour and if it is too crumbly and dry add more water and knead for another 5min.
Place the pizza dough on a lightly floured baking paper, shape into a smooth ball and using well-floured hands and a rolling pin, pat and roll out dough on a lightly floured surface rotating the dough and flouring it frequently, to prevent sticking. Roll and pat the dough more thickly as you work from the center of the dough to the edges to create a crust. Make your pizza crust as thin as desired. (I like my pizza crust quite thin). Put your favorite toppings and transfer the pizza with the baking paper on which you rolled it out, to a baking tray (or I sometimes use baking rack).