I've done the shaping on the previous/following row. For instance, if you're working left front panel (on body) and first BO says to do 3, you'd normally do the 3 BOs on the RS. However, I'd work the RS and then I'd work across WS til I had the 3 remaining, W&T (thereby forcing those to create the slope) and then work back.
In order for the BO sts to be the last sts still remaining on your needle means that you're now on the opposite row from which you'd normally work them. (They're the first sts on the RS, in this case.) Make sense? Hope so.