Backwards up the mossy glen Turn'd and troop'd the goblin men, With their shrill repeated cry, "Come buy, come buy."
The "goblin men" turn around and come back up the valley. They must realize that Laura's checking them out. Maybe they can sense that there's a potential sale to be made here.
They keep crying out their tired old sales pitch: "Come buy! Come buy!"
When they reach'd where Laura was They stood stock still upon the moss, Leering at each other, Brother with queer brother; Signalling each other, Brother with sly brother.
When they get back to where Laura is, the goblins stop and "leer," or glance sideways, at each other.
They're described as "brothers," but don't assume that they're related by blood. As in HBO's Band of Brothers, they're just all part of the same band.
In line 94, "queer" means "suspiciously odd."
The goblins sneakily "signal" to each other.
They're described as "brothers," again. This time as "sly brother[s]." The repetition underlines the fact that they're all members of one group, while Laura is isolated and alone. Even her own sister, Lizzie, isn't around.
One set his basket down, One rear'd his plate; One began to weave a crown Of tendrils, leaves, and rough nuts brown (Men sell not such in any town); One heav'd the golden weight Of dish and fruit to offer her: "Come buy, come buy," was still their cry.
After "signaling each other," the goblins all leap to action, and they all seem to have different, pre-arranged tasks. It seems like they've done this before.
The uniqueness of the individual goblins is emphasized again: like in lines 71-76, lines 97-102 begin with "One" – "one" goblin did this, and "one" did that. They all have different jobs.
One of them "rears," or holds up his "plate," probably to show off the fruit on it for Laura.
Another goblin starts to "weave a crown" for her out of branches of nuts.
Line 101 is in parentheses – it's as though the poet is telling us, just by the way, that the kind of nuts the goblins are using are really uncommon. This seems important, but like a lot of the details in the poem, the meaning isn't clear.
Another goblin hefts up a heavy golden dish full of fruit to offer her.
They're all still "cry[ing]" in unison, "come buy! Come buy!"
This might seem creepy, but Laura clearly has not seen as many horror movies as we have, so she doesn't know that this would be a great moment to turn and run.