I have numerous students who also struggle with this in Nav training, so rest assure your not alone Maggy drop, firstly make sure any knee board you use is on your left leg so you can rotate it out of the way when not required, eg in cct. Secondly go with a smaller one and as DJP says learn to fold the maps down to usable sections, next make sure your board has a clip so you can remove the map and look at it in front of you when orientating your position, ( map to ground)- this ensures you keep your head out of the cockpit!
Last but not least if any system gets in the way of operating the controls then find something else, safety is paramount.