ほう is a noun that literally means side/way/direction etc. So in a sentence like 食べたほうがいい you can think of it like a relative clause with the meaning "the way where you eat" is good., i.e. "you should eat". So this construction isn't quite as special and mysterious as you might think.
In your sentence 明日のほうがよく you can think of it (very awkwardly) as "the tomorrow side is good". Why "the tomorrow side"? Maybe you are given two options, either let's meet tomorrow or let's meet on Sunday. Which 'side' or which option is best? This construction is often used to make comparisons in Japanese. Sometimes より is used to specify what you are comparing with. Sometimes より is not used because the comparisons is implied.
So a translation for your sentence could be:
Tomorrow is better, right?