3X2 stud wall "dry lining" cellar, so "one sided" i.e. rear face not boarded over.

Plan on putting 50mm rockwool bats into the wall before pb-ing over.

How do you ensure the insulation says put? and doesn;t fall out "backwards"..

Musings so far are
1) it'll stay there by wedge power alone,

2)run some strings/gaffer tape across behind the studwall for it to "lean on"

Anyone had a similar quandary and resolved it ?

Cheers
Jim K