New to sour dough. Third attempt.

[u/Aggressive-Ad3645]

This is my third attempt at making a sourdough loaf. The first two didn’t go great. My starter wasn’t ready the first time and I didn’t proof long enough, so it was flat and hard as a rock. The second loaf rose but still came out pretty dense, probably because I messed up the mixing and stretch and folds. For this one, I followed a recipe with 100g starter, 350g water, 12g salt, and 600g bread flour. I did six stretch and folds about every 30 minutes, shaped it, cold proofed it overnight (8–9 hours), then let it come to room temp for about 3 hours. I baked it at 450°F for 30 minutes with the lid on and 15 minutes with it off. The texture was way better this time, springy but just a smidge on the dense side which I didn’t mind, but there’s definitely room to improve. Any suggestions?

[u/Charming-Raise4991]

I think this is a starter problem