In a large bowl, whisk together flour, oats, sugar, salt, and yeast until evenly blended.
Pour in warm water and honey, then stir until a sticky, shaggy dough forms.
Cover the bowl with plastic wrap and let rest at room temperature for 12–18 hours, until doubled in size.
Place a 6-quart Dutch oven (with lid) in a cold oven and preheat to 450°F. Heat for 30 minutes.
Dust a work surface with flour, gently turn out the dough, and shape into a smooth ball by folding edges underneath. Let rest 15 minutes.
Using the parchment paper, transfer the dough into the hot Dutch oven, sprinkle extra oats on top, cover, and bake for 30 minutes.
Remove the lid and bake an additional 15 minutes until the crust is deep amber and crackling.
Lift the loaf onto a wire rack, brush with honey, and cool at least 1 hour before slicing.