How to Tile (Trim) around splashback on a window??

[diyer2011]

unsurprisingly it was me being a div

it'll work if you stand your trim up in your mitre box and not lay it flat.

And here was the solution! I wasn't using a mitre box so it didn't occur to me to cut from a different direction. I grabbed a mitre box and bearing in mind this post it all made sense.

Thanks!