Keeping busy can help some people focus on something outside of the voices. It might be a hobby or an interest, or a specific task that requires concentration, like cleaning or mending something. Or it might just be a daily activity or work.
I wear headphones with music which helps with the voices and do knitting where I count stitches on every row which can also help.
When alone I read and force myself to concentrate on things like word puzzles.
Keeping busy is my main therapy. I run a weekly hearing voices group and do 1:1s with patients at the local psychiatric hospital. I help run day centres for people with mental health issues and am involved as a director of a pan disabilities organisation. I give talks and teaching about hearing voices.