Best way to cut window board

[Psyclist]

The window I need to fit a window board in has unequal adjacent walls and the wall in which the window (or the window itself) isn't straight either so both ends of the reveal are slightly different depths.

The long cut I'm not too bothered about. I can just measure in from the curve on the board at both ends and draw a straight line, but how do I measure the angles and cuts at the ends or what is the best way?

 

[ladylola]

Assuming that you have the reveal plastered which is why you are needing it to be accurate?
Best and simpliest way is to cut some hardboard templates, one for each end for ease then dropped on top of each other and marked to locate them together then simply transfer over to the precious window board.

 

[Psyclist]

Excellent thanks. Yeah the reveal is plastered so I need to get it as tidy as possible.

Is it better to leave ears or is it perfectly normal to just have a straight cut at either end?

 

[ladylola]

Ears every time , looks so much better.