If you want to serve baked oatmeal on a Wednesday morning and have it prepped the night before like how I do it, here's what I do to make it happen:
If you are using ACV or lemon juice, start soaking the oats on Monday night. If using sourdough starter, start soaking the oats on Tuesday morning (you can start it on Monday night, just be warned that the oats will be very sour!).
Tuesday night, after the kids are in bed, drain the oats and proceed with the recipe. After you've poured the oatmeal mixture into the greased baking pan (I use glass), cover with plastic wrap.
In the morning, take off the plastic wrap and pop the pan into the oven. Turn on the oven (yes, after you've put the pan in... so that glass will warm up with the oven) and when the preheat is done, set the timer for 45 minutes. When timer goes off check the baked oatmeal and add more time if needed.