In a mixing bowl, combine the starter, water, honey, avocado oil, and salt until combined.
Add in the flour and mix until combined. It will be shaggy, so use your hands to finish combining it into a dough ball until all the flour is incorporated. (If your dough isn't coming together, add in 1-3 tablespoons of water to help).
Turn the dough out on the counter and knead for 5 minutes by hand or with a bread hook on an electric mixer. If you need, add a little flour if the dough is sticky. Place dough back in bowl and cover loosely with a towel or lid.
Let the dough bulk ferment on the counter for 10–12 hours.
When the bulk fermentation is finished, turn the dough out on the counter (no flour needed), stretch it into a small rectangle, roll it up into a log loaf, and pinch the seam together with your hands.
Place the shaped loaf in a lightly greased 9×5″ loaf pan and cover with a tea towel.
Let it rise in the pan for 2-3 hours on the counter.
(Optional: if you don’t have time, place the loaf pan in the fridge after the 2–3 hours are finished until you’re ready to bake. It can sit in the fridge for up to 24 hours.)
Bake at 375 for 45 minutes.
Immediately after baking, place the bread pan on a wire rack and brush with butter to ensure a soft crust. After 10–15 minutes, remove the loaf from the pan and let it cool the rest of the way.