It's a matter of personal preference.

I have fed many snakes for many years in the cage and have never had an issue with one mistaking my hand for food.

Recently, our vet told us that he had his first case of impaction due to aspen substrate. The snake in question was extremely young, however.

Since then I have fed my young snakes in separate containers sans substrate. I let them relax about 45 minutes after eating and then quickly put them back into their cages. I have not had a regurgitation or any other problems associated with this method.