Put 450 ml of lukewarm water in a bowl and crumble the yeast into it, stir briefly.
Stir the flour into this water-yeast mixture. Then add salt, bread drink or vinegar, sunflower seeds and linseed and everything thoroughly - e.g., using a wooden spoon or mixer - mix together.
Generously grease a box or other bread pan, fill it with the dough and smooth it out a bit.
Bake the bread in a non-preheated oven at 200 degrees, fan-assisted 170 degrees, for 50 minutes. Maybe 5 minutes longer.
Remove the still warm bread from the mold and let it cool down.