I slippedmy feet into themas ifintojewel cases (8-12)
Bust out your toe rings! The socks in these lines give not only the speaker's feet, but the very speaker a new status. If the socks are jewel cases, then the speaker's feet are jewels. This image is about how the socks make the speaker feel, which is, in short, happy.
thus honoredweremy feetbythesecelestialsocks. (27-33)
As in the previous quote, these socks are really making the speaker do the happy dance. The feet here are "honored," which shoes how the simple article of clothing really affects the speaker's state of mind.
twice beautifulis beautyand what is good doublygoodwhen it is a case of twowoolen socksin wintertime. (81-88)
It's hard to think of a better description of happiness than the thought of nice warm feet, heated up by the gift of homemade socks, on a cold day. Unless you could add a cup of cocoa to this mix. With whipped cream. And marshmallows. Mm, marshmallows…