This is where working with natural yeast can get tricky....because this last rise is hugely dependant on the time of year and the weather. First, lay plastic wrap right on top of the loaves and cover again with a towel. In the cooler months, I need to put the loaves in the oven (while it is off) and place a roasting pan on the shelf below them filled with boiling water. Close the oven door and don't open it for at least 8 hours. This usually does the trick.
In the spring, summer and fall there is no need for this extra step. The final rise can happen on a counter in about 8 hours or so.
When the loaves have risen, all that's left to do is bake them in a 350 degree oven for about 40-45 minutes. Test the loaves to see if they're cooked completely by thumping a wooden spoon on the tops - you want to hear a hollow sound.
Making bread with natural yeast is not as difficult as it sounds. I hope this post helps and encourages you to give it a try - and thanks to all the people who stayed for the demo last night!
Enjoy the day -Wonderwoman