There's a bug i noticed that'll probably get fixed soon, so make use of it now. I've only seen it done on floors (constructed and the tops of walls should count) so far, so further !!SCIENCE!! is needed. The floors were wooden, too

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>Embark on an area that's temperate but still cold enough that water freezes every now and then
>Designate frozen water to be smoothed or engraved, but make sure that no-one actually smooths them yet (or if you DO smooth them because you want to engrave them, don't actually engrave them yet.
>Wait for water to thaw, then construct floors over the water.
>Enable engraving labor for Dwarf/Dwarves.
>Floors should get smoothed/engraved.
I only encountered it once, and it was sometime last year, so don't take these steps as gospel.