  Building on an old result of Duncan and Namioka, we show that the
${\ell}^1$-convolution algebra of a semilattice $S$ is biflat precisely when
$S$ is uniformly locally finite. The proof shows in passing that for such $S$
the convolution algebra is isomorphic to ${\ell}^1(S)$ with pointwise
multiplication. At the end we sketch how these techniques may be extended to
prove an analogous characterisation of biflatness for Clifford semigroup
algebras.
