Combine the sourdough starter, molasses, honey, coffee, and water in a large bowl or lidded container. Add the flours and salt, and mix until it forms a thick, sticky dough. Cover the container loosely with its lid, plastic wrap or a damp kitchen towel, and allow it to rise at room temperature for approximately 1 day, give or take a few hours, until roughly doubled in size.
When you're ready to bake, prepare a surface for working with the dough by lightly dusting it with all-purpose or whole-wheat flour. Preheat oven to 400 If you have a baking stone, place it on the middle rack. Even though the next steps take some time, start the preheat now anyway; give the oven plenty of time to get the stone really hot.
To shape the dough, begin by evenly dividing the dough into two halves. Pick up each piece, dust the dough with a handful of all-purpose flour and use your hands to shape it into a ball, creating gentle surface tension by stretching each of the four sides of the dough down to the bottom of the ball (the "gluten coat" technique). Shape the dough-ball by patting the dough into an approximately 1.5" thick rectangle, folding/pressing one edge to the center, rolling the rest of the way, tucking under each of the two ends, and pinching the seam.
Place the shaped loaves on a piece of floured parchment paper placed on a large cutting board (or pizza peel, or other sturdy, rimless platter). If you won't be using a baking stone, place the parchment onto a large sheet pan instead. Brush the loaves lightly with water, and sprinkle with oats. Cover loosely with plastic wrap and rise in a warm place for about 30-45 minutes, until the loaves have begun to plump.
Use a sharp knife to score the proofed bread, slicing into each loaf with 2-3 shallow cuts (approximately 0.5" deptat a 45 degree angle. Open the oven and carefully slide the loaves along with their parchment liner onto the baking stone (or transfer the sheet pan). Bake the loaves for about 40-50 minutes until they are deeply browned; doneness can be tested by knocking the loaves bottoms to listen for a hollow sound, or measuring an internal temperature of at least 190 Let the loaves cool on a wire rack, and wait until they are fully cool before slicing or storing in any kind of container; paper bags recommended for storage.