On The Phenomenology of Spirit (1807), ch. 1 "Sense Certainty" and ch. 2 "Perception." After introducing Hegel's project in ep. 275, we now walk through the first two steps of his dialectic where he presents some basic theories of knowledge and shows why they're inaccurate.
The first of these is direct realism, the idea that perception is a simple matter of being directly exposed to particular things. On this view, we don't need to know what the thing is exactly, and we don't need to talk about it. We just sense it. Is this a reasonable view? Hegel says no: In trying to pick out what it is we're sensing (even nonverbally, just to ourselves), we have to use something like pointing, i.e. the concept of a "this." What goes into picking out a "this"? Well, we need a notion of "here" and one of "now," and all three of these notions on closer scrutiny are universals, meaning that they're general concepts that refer not just to that one thing you're trying to pick out, but to any number of instances of this, here and now. (The modern term for these concepts that vary systematically in meaning according to the circumstance of their utterance is "indexicals.") We thought at the beginning of this "sense certainty" stage that there's really no philosophical problem to perception at all, and by the end we find that perception is going to require concepts, that there's really no such thing as just raw sense data that can then provide a foundation for perception.
In the second stage, we've admitted that there are concepts, but these concepts still function to pick out sensible particulars, like a particular piece of chalk in front of you. Is there something problematic about this idea of a conceptualized sensible particular? Well, yes, there's something paradoxical about the relation between this substance and its various properties. As Locke famously pointed out, we don't actually have a good idea of what this bare, propertyless substance might be at all. So is this substance really a One, a single object? Or is it an Also, i.e. a bundle of properties that sit together in this indefinite medium. By the end of the section, Hegel will posit that to make sense of this relation, we need the idea of "force," i.e. something unseen that captures the dynamic interplay between visible properties. We're no longer by that point talking about sensible particulars at all, but about events that we attribute to unseen forces like gravity and electromagnetism. We'll talk about that third (pretty complicated) step in the dialectic in our episode 277, which will serve to wrap up our treatment of this book (for the moment).
There are many more twists and turns in the argument than I've indicated here, but hopefully we walk through them step by step slowly enough in the discussion that you don't get lost. Given that Hegel is so steadfastly against the idea of merely summarizing philosophy as opposed to actually doing it, it's not surprising that it should be difficult to do so adequately here.