That's a myth. Feeding them within their own enclosure won't cause them to associate your hand with feeding, nor cause them to bite because of that. Feeding in a separate container does work for some people because their snakes are used to it, but with a new BP, I would highly recommend just feeding it within its own home. That way, the territory is familiar, their hides are right there ready to retreat to if they feel the need, and when they are done eating, there will be no need for you to disturb them at all.