Mix flour, yeast and salt in a large bowl. Add warm water to the ingredients and mix until a sticky dough forms.
Cover with a towel and let it rise on the counter for 12 to 20 hours.
Preheat the oven to 500F/260C. Turn your dough out on a floured surface.
It will be flat, tuck all four sides in to form a ball and place it on a floured towel seam side down, sprinkle with more flour. let it rise for 2 more hours in order to produce a more airy loaf of bread.
Preheat your oiled dutch oven with the lid on. Take it out of the oven and carefully place your dough in it.
Cover with a lid and bake for 30 minutes.
Take the lid off and bake for 10-15 minutes longer to get more colour into your crust.
For the multigrain option:
Put all the ingredients for the multigrain mix in a bowl, including the water, and stir to mix.
Set aside for one hour.
Add the multigrain mix to the no knead bread dough, just use a wooden spoon to stir it into the dough.