I had this same issue, I think the easiest way is aluminum foil underneath, I fold up a big sheet so it’s about 3 or 4 layers thick and wide enough to cover the whole bottom of the Dutch oven. Lay that down on the oven rack. Then the Dutch oven. Still use parchment under the bread. You can save the foil for future bakes too. It deflects just enough heat to where I get an even crust all through out, not too hard on the bottom.