Mitering the edges of two panels that but up against each other is the best way to create a stone facade appear seamless.
Here's a quick tutorial on how to cut corners that you can be proud of!
To miter a panel on your own you will need:
A Power Drill
Caulk (preferably a color that will blend with your panel)
ATable Saw or Circular Saw
Measure and mark the end of your panel. Remember to measure twice, maybe three times, and cut once.