In article , Rusty Hinge
writes

Cut beans and put them into just enough boiling water to cover them.
Bring back to the boil and seeth for two and a half minutes. Cool the
beans in the water and put beans into freezer bags. Add the water you
blanched them in, knot bags and freeze.

That is a perfectly acceptable way of freezing runner beans. Our way is
somewhat simpler though. We pick the beans quite young and tender, well
before any stringiness is forming. We top and tail them, slice them,
pack them flat into freezer bags and pop them into the freezer within
minutes of picking. They come out almost as crisp and tasty as they went
in and they are easily separated in the bag if only a small quantity are
required. We have done that for many years with excellent results.
--
Alan & Joan Gould - North Lincs.