Activate the Yeast: In a small bowl, combine warm water and sugar (or honey). Stir in the yeast and let it sit for 5–10 minutes until foamy.
Mix the Dough: In a large bowl, combine flour and optional flaxseed. Add in the foamy yeast mixture, olive oil, and apple cider vinegar. Mix until a shaggy dough forms.
Knead the Dough: Turn the dough out onto a floured surface. Knead for 8–10 minutes by hand, or 5 minutes with a stand mixer until smooth and elastic.
First Rise: Place the dough in a lightly oiled bowl. Cover with a damp towel or plastic wrap and let it rise in a warm place for 1 to 1.5 hours, or until doubled in size.
Shape the Loaf: Punch down the dough, shape it into a log, and place it in a greased 9x5-inch loaf pan.
Second Rise: Cover and let the dough rise again for 30–45 minutes, until it just peaks over the edge of the pan.
Bake: Preheat your oven to 375°F (190°C). Bake the loaf for 30–35 minutes, until golden brown and hollow-sounding when tapped.
Cool: Remove from the pan and cool on a wire rack for at least 1 hour before slicing.