Why does my homemade sourdough bread always fall flat, even after proofing for hours?

I totally feel your frustration - it's disheartening when your bread doesn't turn out as expected, especially after putting in so much effort. I've been there too, and I've found that one of the main reasons for a flat sourdough is overmixing the dough. When you mix the dough too much, you develop the gluten in the flour, which can lead to a dense and chewy texture instead of a light and airy one.

So, how can you avoid overmixing? For me, the key is to mix the ingredients just until they come together in a shaggy mass, and then let the dough rest for a while. This is called the autolyse phase, and it allows the flour to absorb the water without developing the gluten. After that, you can do a few gentle folds to distribute the yeast and starter culture, but be careful not to overdo it. I've also found that using a stand mixer with a dough hook attachment can be helpful, as it does the work for you without overmixing the dough.

In terms of your oven and mixing techniques, it's possible that these could be contributing factors, but I think it's more likely that the issue is with the dough itself. Have you tried checking the temperature of your oven with an oven thermometer? Sometimes, ovens can run hotter or cooler than the temperature you set, which can affect the rise of your bread. Also, make sure you're not overproofing the dough - if it's rising too much, it can collapse in the oven and end up flat.

I hope these tips are helpful, and I'm sure you'll get there eventually - making sourdough is all about experimentation and practice, and it's normal to encounter setbacks along the way. Don't give up, and keep trying - I'm sure you'll soon be enjoying delicious, light and airy sourdough bread, fresh from your oven. Good luck, and happy baking!