The word "still" gives us a lot to chew on. The poem opens by letting us know that the speaker is still in the orchard, up on his ladder. But is he really, or is he just reliving the day in his memory? He seems to be taking a disorderly mental trip back through the experience of apple-picking.
But I am done with apple-picking now. Essence of winter sleep is on the night, The scent of apples: I am drowsing off. (line 6-8)
Again, the simple statement, "I am done with apple-picking now" has different levels of meaning. It could mean, "I'm tired of this, so I'm hanging it up for the day." Or it could be a simple factual statement to remind the reader that the speaker is thinking these thoughts after he is "done" with apple-picking and is lying in bed for the night.
I cannot rub the strangeness from my sight I got from looking through a pane of glass I skimmed this morning from the drinking trough And held against the world of hoary grass.(lines 9-12)
The memory of how the icy ("hoary") world looked through a pane of ice remains fresh in his mind throughout the whole day. He tries to "rub" this strangeness from his sight, as you might do when your eyes are watery.
And I could tell What form my dreaming was about to take. (line 16-17)
Just on the basis of his memories of the day, the speaker knows what he will dream about. Strictly speaking, we're pretty sure you can't actually predict your dreams like this. He's making a rhetorical point.
My instep arch not only keeps the ache, It keeps the pressure of a ladder-round. I feel the ladder sway as the boughs bend. (lines 21-23)
The speaker makes a subtle distinction between active and passive forms of memory. A passive form of memory would be the "ache" that reminds him of standing up on the ladder all day. But he also feels the more active, present memory of the ladder pressing into his foot. He truly is reliving the day again.