Mix the ingredients for the starter and let it rest at least 6 hours, better over night. There should be lots of bubbles in the starter after that.
Add the other ingredients to the starter and knead for 5 - 8 minutes.
Let the dough rise for the next 3 hours with deflating it every hour. During that time leave the dough in a bowl and cover it with a towel.
Divide the dough in 3 pieces and let them rest for 15 minutes.
Flatten the dough to an oval and fold it twice. Do it with each piece of dough and put them on a baking sheet. Cover them with plastic wrap and leave them alone for another 1.5 hours.
Heat up the oven to 450F/235C. With a sharp knife cut 3 slashes in each baguette. Spritz them with warm water before putting the baking sheet into the oven. Use the middle rack.
Bake the baguettes for 25 - 30 minutes until the crust is golden brown. Take them out and let them cool on a rack.
Enjoy your french baguette!