Enacaustic cement tiles on wall

Hello, very grateful for any help. I have some encaustic cement tiles 13mm thick that I want to use as a splash back, 1m x 1m behind a cooker.

What thickness of adhesive should I allow as I want to put a straight edged tile trim on the edge , I am thinking an 18mm metal trim will be sufficient, ie, 5mm of adhesive.

Also what ready mixed adhesive would anyone recommend for this type of tile.

D