Trimming a window that is out of square
I want to trim a exterior garage window - essentially just "picture frame" it so it ties in more with the house. I plan using trim molding cut at 45 degree angles. Took all the height and width measurements and they are the same top to bottom and side to side. I'm not an experienced woodworker by any stretch of the imagination, but do know enough that in order to use 45 degree angles, the window that I want to frame must be square. It's not - off by 1/4". How do you account for this when planning the miter cuts? Or, do you just cut the pieces and take the difference into account when you nail up the trim pieces, filling the gaps in with caulk.
Any advice will be greatly appreciated.