If I were you I would make the cut at a portion with full diameter. It will probably branch at the top, quite possibly several branches. If you make the cut where it is skinny there will be very little room for branches. If you cut at a slant it will most likely pup from the highest areole/s first. Try to make your slant cut so that it is a few millimeters above every areole. In my experience this is the optimal hieght to produce pups. Flip's recomendation looks great to me. It appears the bottom cut would be basically into the full diameter portion of the base, and that etiolated tip will make a decent looking specimen when you plant it on it's own. I would plant them all vertically too.
Peace.
