My next assignment at a friend's new-used house is to cut some ready-made
Home Depot countertop to correct length, and cut the hole for the sink. I've
got some concerns, mostly due to the fact that I've never done this before
and it's her money.

The pieces will have a backsplash. Cutting a flat piece of countertop seems
easy, if all precautions & preparations are done right. But, continuing the
cut to wrap around the backsplash seems dicey. I'll be using a sabre saw and
I envision doing the cutting from the bottom, as mentioned in the brochure.
I assume it's done this way because the sabre saw blade cuts on the
upstroke, so the teeth won't be trying to push the laminate off the
underlying board.

What's the trick for the backsplash? Cut from the top edge toward the
counter, then cut from the counter's front edge toward the backsplash, and
then join the two cuts (while praying)? Maybe finish that cut with a keyhole
saw? My friend will be buying the end cap kit mentioned in the brochure, but
I don't know yet how much fractional error these kits can cover up, if any.