You can use a router with partial templates when cutting out the main side panel template. What I mean is, say you want consistent rounded corners. You can make a single rounded corner using a jigsaw/bandsaw/etc and sander on a small piece of wood, then clamp that to your main panel template and use a router w/ a flush trim bit to trim it to that shape.
Then you use the small template to do the same with other corners. When you are done, all your corners will be the exact same shape. Note that you'll need different templates for inside corners versus outside ones, or if the corner edges have different angles.
Same thing with straight edges. You can use a single straight edge, clamp to a section of the main panel template and route it. Then clamp the straight edge to another section of the main panel, and repeat.