There is an old contractor's trick when installing kitchen cabinets to make sure the counter is cut to match a wall that is not as perfectly square the rest of the counter. It is using templates. Some call this method "Story Pulling" (and the extra nerdy would correct them by saying that templates are not real story pulling).
Making templates you will need:
* 1/4 or 1/8 plywood cut in approximately 2 inch strips. This is most easily done on a table saw.
* A hot glue gun and lots of glue sticks. Any cheap glue gun will work.
* A utility knife.
1. Have your supplies ready. Plug in your loaded glue gun, stare at your surface, scratch your head.
2. Pick up a strip of plywood and strike a cut mark in the plywood as if you were going to cut two inches off. You will find that the plywood will break off at your strike mark.
3. Glue that little piece of plywood on the surface you want a template from.
4. Glue another piece of plywood to both the original piece of plywood and the surface. Just a little glue on the surface and emphasize more glue between the plywood pieces (so it holds together when breaking off your finished template).
5. Repeat steps 2 through 4 until you have your template.
6. For good measure add more glue to the plywood joints so the template does not fall
apart when removing it.
7. Gently break off your template and you have a something nice you can trace.
Tip # 1 You can use a strip of floor linoleum to press along your template to make a smoother line.
Tip # 2 For long templates, cut a piece of plywood in the ball park shape of your surface so your template has a stronger spine. Really long templates easily fall
apart when you remove them from their surface.
The second tip was discovered when I first tried to make the bedroom arch using a template that fell apart when removing it. The first piece I cut was off but that first piece made a really nice foundation for template for the second try. Also when using plywood, you can also use a finish nail gun to stick the pieces on.