How do you encourage branches to grow on bald stems?

Ayrshire, Scotland Sco

I used to have 2 camelias right next to one another and pruned one hard - to about 18 inches hoping it would come back a better shape, however unfortunately it didn't recover!

My problem is with the remaining camelia, because it had been growing up against the first camelia it is now bald all down one side of the stem - beautiful and bushy on the other side and just started to flower.

Can you please advise how I can maybe get stems to grow again from the bald side - I think I saw Joe Swift on Gardener's World saying you can saw into the bald stem, but don't know how many cuts or how deep to do it.

Do you know and can you help please.

Many thanks in anticipation.

On plant Camelia Japonica