Tiling around a window

[Kossie]

I am fitting 6mm deep 10cm sq rustic tiles around the lower part of a kitchen window. My question is - where do I position the overlap and how do I tile into the corners? (I don't want to use plastic edge strips) Should I inset the top surface or overlap it (if you know what I mean?!)

[Moz]

hello Kossie
if I read you right
I would tile then have the tile overlap it so there is no top grout line on the sill