Can use any fleshy black olive in place of Kalamatas.
In a bowl, dissolve the yeast in the water. Allow to proof for three minutes.
Stir the sponge into the water, breaking the sponge up using your hands or a spoon.
Add 3 1/4 cups of the flour and salt and mix, scraping and folding until the dough gathers into a single mass. Mix in the olives and thyme until distributed. This dough will be wet and sticky.
Turn the dough out onto a lightly floured surface, and knead as much of the 1/3 cup of flour as is required to make a smooth and elastic dough.
Place the dough in a lightly oiled bowl, cover with plastic wrap and refrigerate overnight.
Halve the dough and shape each piece into a ball and place in an oiled bowl and cover with plastic. Allow to rise in a draft-free location for two hours.
Turn out each piece of the dough onto a lightly floured work surface and press out any large bubbles. Shape each half into a loose oval. Transfer each of the ovals into a 9x5 loaf pan, with the seam on the bottom. Cover again with plastic and allow to double in bulk, which should take 2 to 2 1/2 hours.
Preheat the oven for at least thirty minutes along with a baking stone or tiles on the middle rack to 425. Place a baking pan with decent sides on the bottom shelf. Boil two cups of water. Place the loaf pans on the stones and then immediately pour the boiling water into the baking pan.
Bake for 35-40 minutes until the loaves are hollow sounding when removed from the pans and tapped on the bottom. Take the loaves out of the pans and cool on a rack.