Boil 250 ml of water in a saucepan (I always use a kettle for this, it saves time), then add a pinch of salt and a little sugar to the water. Put 2 - 3 heaped spoons of the oat flakes in the boiling water and cook them for 5 minutes, stirring constantly.
I always refine my porridge with homemade jams and dark or white cocoa powder.
You are also welcome to replace the oatmeal with semolina or polenta (for a little variety, but then needs more time to cook).
Many add a sip of milk and a little butter. It would be important that the butter is cold when you add it and no longer boil, so assemble the porridge like a risotto. If you do, the porridge is no longer vegan.