Since I learned a lot by reading other peoples' posts, I thought I'd share my experience.
This was a preformed countertop with the integrated backsplash. It required a 10' length and a 6' length joined at a 45-deg seam. Despite the recommendation of many people, a circular saw was not the best tool for cutting the countertop. If your cut happens to not go exactly along the cut line, it is very difficult to change the direction of the blade. The blade will bind and burn the wood. A jigsaw works much better. Cutting the backsplash is a bit tricky, but the jigsaw allows enough maneuverability to do this relatively easily. I don't know how people do this with a circular saw. Use a fine toothed jigsaw blade to avoid chipping the laminate. A masking tape might reduce the amount of chipping. It is best to make the cut slightly beyond the cut line and then sand down the flanges. I wasted many hours trying to sand this with the average finishing sander. Even with the coarsest grit, it won't even make a dent in it. Get a belt sander. It will melt away the material quickly leaving a smooth flange. Just be careful not to sand away too much.
The 45-deg cut requires a lot of patience with a tape measure, ruler and calculator. Since the counntertop ends are rounded off, it is hard to get an exact measurement to draw the 45-deg line. Even a millimeter error will make a visible gap in the seam, so it is well worth spending some extra time to confirm the measurements before taking the saw to it. Again, cut slightly longer than necessary and sand it down.
The location did not allow me access to the underside of the countertop at the 45-deg joint. This meant that I could not use the countertop bolts to join the two pieces. Instead, I screwed a length of plywood to the underside of one countertop, set the next countertop butted against it and glued the two pieces in place using strong fiberglass epoxy. The disadvantage is that it would be impossible to take the two pieces apart in the future without breaking them.
Finally, cutting the hole for the sink and installing it was the easiest part.