Loaves Are Flat (Updated!)

Hello All,

I've been a silent forum reader for several years now while I've been on my sourdough journey. After all of these years, I still can't seem to get proper ovenspring out of my boules.*

So here I come to you, with meticulous detail, about my formula and process in hopes that perhaps you can help find a solution. 

I've used the standard Chad Robertson's Country Loaf, using 500g TFW to shape two small boules.

Here is my process chart with time, temperature, and notes, which I will go into more detail about: 

So, I fed the starter with a low inoculation, as Chad does, and let it ferment until it passed the float test.

I mixed, autolysed, and began doing turns every half-hour, starting aggressively, and then moving to more gentle turns as the dough developed until it passed the windowpane test.

I bench the dough and preshaped, (it held it's shape beautifully, better than I've ever seen,) after 25 minutes resting.

I shaped and then retarded the dough in homemade banneton baskets lined with floured linen at 45 degrees Fahrenheit for close to 8 hours.

I removed the first boule while preheating the oven to 500 degrees F and cast iron combo cooker for 25 minutes to come up in temperature before baking.

I scored the loaf and baked 20 minutes covered and 20 minutes uncovered @ 450 degrees F. 

The boule was flat.

The second boule, I thought I'd let come to temperature and finish proofing for a little over an hour @ ~80 degrees F ambient temp, as I thought the first boule had been underproofed.

Baked 20 minutes covered and 20 minutes uncovered with similar results as the first one.

So, with all of that, what could I be doing wrong?

• Perhaps I'm very bad at shaping the dough?
• Maybe my dough is underproofed? Overproofed?

Thank you guys for taking the time to look through all of this information. As I hope you can see, I've been trying very hard to narrow down the variables at play here by keeping meticulous details. Any suggestions??

In terms of taste this is one of the most beautifully complex breads I've ever baked.

I've baked several dozen loaves over the years and I've experienced pretty much the same results. I'm not always a bake-by-numbers baker, but I try to take meticulous notes to quantify what I'm experiencing in hopes of better troubleshooting. Anyone love looking at this data to find errors or possibly more variables I'm missing?

*Except for an enriched sourdough that contained buttermilk, oats, and honey.