In a large bowl or square container, mix together the flour, yeast, diastatic malt powder, and salt.
Add the water, poolish, olives, rosemary, and olive oil and mix by hand to combine. Stretch the dough to thoroughly mix it. This should take about 5 minutes to mix. Take your time. Cover and let the dough sit for 60 minutes.
After 60 minutes bring the dough to a floured work surface and lay it out. Using a dough scraper with a bit of bench flour get under the dough and pull it to stretch then fold the dough over itself and rotate it 90 degrees. Stretch and fold the dough 3 more times while rotating after each stretch and fold. Use the scraper and gently place the dough back into the container. After 30 minutes, do another 4 stretch and folds. Note: You can also stretch and fold the dough right in the container. To do this dip hands into a bowl of water before each stretch and fold. Either way works fine!
Being gentle to not degas the dough, form a round loaf shape. Place the dough ball seam side down into a bowl lined with a piece of parchment paper. Cover with a towel or plastic and let it rise for 90 minutes or until it approximately doubles in size.
45 minutes before baking, preheat the oven to 450f and set the rack towards the middle level leaving enough space to hold a Dutch oven with its lid. Place a 5-6 quart covered Dutch oven onto the rack and close the oven.
Right before 45 minutes have elapsed, score the dough with a 1/4" deep slit running the length of the loaf at a shallow angle.
Remove the Dutch oven from the oven being careful to avoid burning yourself. Remove the lid and quickly grabbing each side of the parchment paper place the loaf with the parchment paper into the Dutch oven and cover. Place the Dutch oven into the oven and bake for 30 minutes.
After 30 minutes remove the Dutch oven's lid and let the bread bake for another 25-35 minutes. The loaf is finished cooking when it feels hollow when knocked on. If it doesn't feel hollow, simply place the loaf straight onto the oven rack and bake for another 5 minutes and check again.
Once finished baking, place the olive bread onto a wire rack to cool and wait at least 90 minutes before slicing. Enjoy!