It's used in March, because its shape resembles a sweet that is popular in March.

Miya showed the 総荘 by putting both 茶碗 and 棗 in it; but MS puts the 棗 in, and the 茶碗 on top.

The 柄杓 is arranged on it as always: ⅓ where the cup is, ¼ where the handle is.