  We present preliminary results on the reconstruction of the $B^0\to J\mskip
1mu / \psi\mskip 2mu K^0_{\scriptscriptstyle L}$ decay, where $J\mskip 1mu /
\psi\mskip 2mu\to\mu^+\mu^-$ or $e^+e^-$. Using a dataset corresponding to a
luminosity of $62.8\pm0.6\mbox{fb}^{-1}$ collected by the Belle II experiment
at the SuperKEKB asymmetric energy $e^+e^-$ collider, we measure a total of
$267\pm21$ candidates with $J\mskip 1mu / \psi\mskip 2mu\to\mu^+\mu^-$ and
$226\pm20$ with with $J\mskip 1mu / \psi\mskip 2mu\to e^+e^-$. The quoted
errors are statistical only.
