First, focus on your sourdough starter to get a more open crumb for this sourdough bread: it should be refreshed (fed) often, kept warm, and used when ripe.
First, focus on your sourdough starter to get a more open crumb for this sourdough bread: it should be refreshed (fed) often, kept warm, and used when ripe. Next, strengthen the dough sufficiently during mixing and bulk fermentation by using stretches and folds. Finally, your dough must be fully proofed so that when you press a finger into the dough, it slowly springs back about halfway (if it springs back quickly, let it proof longer; if the finger indentation stays, bake immediately).