I actually have done it on the stovetop, but yes, WAY easier in the slow-cooker. On the stovetop, turn the heat off and let the residual heat in the oats cook while you stir, then turn the burner back on low to finish cooking--the residual heat is usually enough to start it cooking, but not to finish. To reheat I add a little water if they've gotten too thick and then microwave--once the egg whites are mixed in the mixture is pretty resilient. I keep them dished up in pint wide-mouthed mason jars until it's time to eat.

Oh, also--this doesn't work, IMO, unattended. You have to give the oats a good stir every hour or so while they cook, even before the egg whites get added at the end, or you end up with oat tahdig. So. No overnight oats on this approach, but still p low effort.

:)