L
LM
Everyone will have different preferences, however the op asked for instruction as to how to do it, I've obliged but that doesn't mean I'm suggesting a novice should be tackling themthis was just an example maybe a bad one but was trying to suggest to mitre the trim from the wall to top trim rather than mitre the top trims together just looks better, also i think that a novice at tiling would find it very difficult to do a three way mitre