I've noticed that English native speakers sometimes omit the definite article before the word class when they ask how it was, even though it's clear what class they are talking about. So, let's say a friend of mine knows that yesterday I had math class and he wants to know how it was. Would there be any difference in meaning betwee the question how was class? and how was the class?
"How was class?" sounds like a question about one of an ongoing series of classes as part of a longer course, like a a university course, or about several classes someone took in one day, like an elementary school. "How was class today?" is another common way of asking this question. Because it's about one of a series of classes, it's likely an inquiry about the student's (or teacher's) experience of the class compared with other times.
"How was the class?" sounds like a question about a single stand-alone class, not taken as part of any broader program. It could be about the experience of taking the class, or about the quality or content of the class itself.
I don't think I would use class that way (without an article) myself, but I wouldn't find it odd to hear it.
It follows a pattern of referring to places or events that are (examples of) an institution.
We have the well known examples to/in church, to/in prison, to/in/at school (at school is more common that in school in British English), to/in hospital (not in American English).
But there are other examples where it is not a geographical location, but an event. I have said that I don't think I say to/in class myself, but I certainly do say to/at choir, to/at rehearsal, and to/at (dance) practice. I've also heard at playgroup, at scouts, and at graduation. Not to mention to/at dinner.
But there's not much obvious logic to this. I don't believe Americans say in hospital (as I mentioned above). And don't think anybody says at lecture, to station, at office, in park, or at beach. It does appear to have to be a regular event: nobody says at wedding, and if I hear somebody say at meeting, I think they're either a Quaker, or a council member in a union.