Please help with the meaning of seal calligraphy writing on the following clay board.
I'll give a slightly different transcription, and a rough translation:
用㠯（以 > 已）
*As @水巷孑蠻 pointed out, this is probably 「姓」.
The Jiǎshēn Palace graces our lands, bringing happiness and fortune to the people; its embellishment, prompted by a call to Royal Favours, gifting the palace with (...), kilned ceramic vessels, bowls, wine cups, incense burners, and wash basins, amounting to 369 items. These are provided to the Palace for the enjoyment [of its residents].
Notice of the vast generosity of Imperial Favours
Jiǎshēn Palace is presumably the name of the palace of the mother of Emperor Gāozōng of Sòng. The palace gained this name, reflecting the day of Jiǎshēn, when Gāozōng held a birthday ceremony for his mother. See e.g. 瓷器有「甲申殿」落款嗎？它又是什麼意思？又代表著什麼？ - 壹讀.
Note: I cannot find the text that you've presented anywhere - this is probably a complete fake.