Yes, cover the entire tuber/corm as roots form all over it, they need to do that. My species are coming out of dormancy here, I will have to put them under lights soon to keep them going, it's too cold here to go into the greenhouse. I don't know your growing conditions but I would remind you that the tubers need long days or they may try and go dormant again. It's the same care whether for the tuberhybrida or species begonias.

Hi
Thanks for the advice Woebegonia it is much appreciated.
Peter