Frankly, most corn snakes will eat just about anywhere with no problems. I usually use a feeding tub, but have also fed mine in their enclosures, especially when I've been sick and warming a mouse was more than enough effort.
A healthy, acclimated corn snake will do fine with the brief and gentle transfer if you feed outside the enclosure. If you are concerned about substrate on the mouse in the enclosure, make sure the mouse is dry or serve it on some kind of plate or plastic lid.
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