In the cage. If you only feed in the cage, the only place the animal is going to be "expecting" food is inside his cage. You could probably get away with feeding somehere else when the retic is small but once the animal is 10, 15 or 20 feet you're not going to want to try to move it around. specially while it's in "feed mode". I've had my calmest retics nail hooks and tongs when they're in feed mode.
Buy a hook or something similar and tap the snake on the head or rub its neck the first time you go into the cage when you're about to handle it. The snake will learn that this means its handling time and not feeding time. Good luck.