I flew aircraft with yokes – Cessna 152, Warrior / Arrow – and used an A4 landscape kneeboard across my lap with no problems.
I flew aircraft with sticks – Bulldog, Pup, Yak 52 – and used A5 sized kneeboard strapped on left leg or left flying suit pocket with a chinograph with no problems.
Maybe a sidestick aircraft like a Cirrus might be more off a challenge. As has been said, trimming properly will help.
As an aside, over the years I reckon that I have met a greater than average number of pilots who are left-handed.