I have two hives currently and am thinking of transitioning to foundationless. I have read that it is important to have the hives level so the comb gets built straight. I am wondering though, if I transition just a couple of frames at a time, is it still important to be level? So, if I remove one frame and replace it with an empty foundationless frame - won't the bees build straight comb simply because there is already straight comb on both sides, even if the hive is not level?
Also - once all the frames are full of comb - is there any continuing need to keep the hives level?