pkoby
I'd call that =paving_stones, but sett is probably also not wrong, according to their descriptions and examples on the wiki. Paving stones wiki says "A relatively smooth surface paved with artificial blocks (block pavers, bricks) or natural stones (flagstones), with a flat top. Sett says "Sett paving, formed from natural stones cut usually to a regular shape. The stones do not cover the surface completely, unlike surface=paving_stones."

See also "Crazy Paving" here: https://wiki.openstreetmap.org/wiki/Talk:Tag:surface%3Dpaving_stones