Finishing the heel?

So, I almost completed a pair of slippers(pattern).
It sais to “whipstitch” the heel. Now, I think I know what that means, but is there a better way to finish? Or, if I use the whipstitch should I do it on the right or on the wrong side?

I vote wrong side…
Whip stitch is just a simple in the front/out the back stitch.

What cute slippers. I would do it on the wrong side too.