Put one cup of flour in a bowl. Add oil(if desired) and half a cup of water and mix with a spoon. When there is no more water visible, stop mixing. Cover the bowl and let it rest for 30 minutes. If you are a beginner and don't know how much water the flour will take, I recommend to add water as you go.
After 30 minutes, add the salt(optional), gently mix the dough for 2 minutes, just enough to gather the dough into one piece. Cover the bowl and set aside for 30 minutes. I usually don't let the dough rest this long. But for those who are new to making roti, will find hard to manage with soft dough. So These additional steps are added. I usually make the dough in one shot, let it rest for about 10-15 minutes covered and prepare the rotis.