I feel like Zoro's three sword style and facility with counting would be a very transferable skillset when it comes to making socks.
So now I headcanon that whenever he's got downtime not training or napping or bickering with Sanji, Zoro settles in to make socks for the crew.
The first pair he ever makes is actually for Nami. They are a little too big in that way that is actually perfectly slouchy and comfortable, and she secretly adores them and wears them on chilly nights while map making.
...I think he probably learned knitting from Perona, actually? So maybe he has socks for the whole crew when he gets back to Sabaody. Except Luffy, and Frankie, who obviously wouldn't wear them. And Brook, whose sizing he couldn't figure out (what would you even measure??). Those three get scarves.
He honestly tried to still make socks for Chopper, but... Well. There were obvious challenges to making socks for something furry and with hooves. He wound up making leg warmers. They have little snowflakes on them.
Usopp's socks are basic, with a bold horizontal stripe pattern in goldenrod yellow, reminiscent of the color of Sogeking's mask. Perona INSISTS on making some cute little felted sheep bobbles to go with them because the socks are Not Cute, but Zoro is too embarrassed to attach them. They become a bag charm. Zoro specifically tells him it's from Perona and smirks when he goes pale.
Robin's socks are better fitted, and slightly more elegant than Nami's, since he started on them so much later in his learning process. They have a whimsical floral motif, and are made from a yarn Perona picked out for her. It is quite possibly the softest thing Zoro has ever touched, and the socks feel like clouds when they're finished.
The real challenge turns out to be making socks for the cook. Sanji is fussy about his clothes, and Zoro knows how hard he is on his feet. He ends up making a very basic pair of suit socks in a deep, rich blue so dark it's nearly black... It takes him three times as long to make them as any other pair he's made, because he keeps starting over.
In fact, he's still working on them on the boat back to Sabaody. He finishes just in time, and Perona steals them away and wraps them up like everyone else's gifts before he can start over again. The first time Zoro sees Sanji light his own foot on fire, he winces and reconsiders whether he should even give them to him. But in the end he does anyway.
(Of course he also made socks for Perona and Mihawk. You think Perona taught him to knit for no reason? Hers are THIGH HIGHS, for fuck's sake! They took FOREVER.)
