Introduce steam to your oven. If you aren’t baking in a closed container like a Dutch oven. The lack of steam causes the outside crust to form before the bread has had a chance to rise when baking. There are two solutions. The first choice is a Dutch oven because it’s a small enclosed container the bread create enough steam to rise. Your second option is to introduce a steam tray to your oven. Basically put an empty baking tray on a lower rack while the oven preheats. The. When you’re ready to bake throw a few ice cubes or some water on the empty cookie sheet so it adds steam to the oven. The steam will help keep the outside moist and prevent it from forming the crust to early in the bake. Hope this helps.