What causes these huge holes and flat loaf?
I've recently started baking sourdough and this is my 5th sourdough loaf but first time using this recipe from theperfectloaf and it seems to have come out very flat and with huge holes in the middle but the crumb is very soft and nice.
I fed my starter and used it the next morning for the levain, is this what caused the issue?
I used marriages very strong Canadian white flour which is 14.9% protein so I assume there's no way it wouldn't be able to handle the hydration of the recipe?
I cranked my oven to the max which registers as 250C in a gas fired oven and I used a 6qt oval Dutch oven that preheated for an hour. I kept the lid on for all 50 minutes as I was trying to make a softer crust for my parents
Apologies if I'm missing any information this is my first post so I'll add any information required!
You didn't mention the hydration level. From the pictures it was very high. In those cases, gas from fermentation will tend to rise and collect near the top. The second picture seems to show that.
For very high hydration, say 80 - 100%, one standard way to deal with that is to proof the loaves upside down and invert them just before baking. The large gas bubbles start to rise and get caught midway during baking.
It's hard to prevent high-hydration bread from spreading sideways. You have to learn how to handle the dough - for example, look on line for videos on making "glass bread".
If your hydration is not all that high, then the holes are a shaping issue. Parts of the dough aren't being induced to merge with the adjacent parts, and that can lead to large holes. The spreading would be about not developing enough gluten during fermentation, or not doing an effective job of tightening up the loaf during shaping.
TomP
Simple really - don't let the holes get that big before cooking. Enjoy!
Your fermentation times are off, your gluten development is insufficient, and you use waaaay too much water.
I briefly reviewed Maurizio's recipe that you linked, and it is just about the same method that I use every day and I have made tens of thousands of loaves over the last 10 years. In fact, I made 300 pounds of this today.
With that as my context, at a glance at your pictures you did not bulk ferment long enough. Your shaping might be subpar too, but that doesn't really matter if you do not bulk ferment long enough (which you did not). I suggest using warmer water or just leaving it out longer to rise. You probably needed another hour of proofing.