Best way to put 10mm ceramic tiles on floorboards

Do not tile direct to floorboards unless you want to waste your money, you must overboard with cement backer board (not plywood that's a thing of the past and is always problematic) make sure the floorboards are fixed solid then glue and screw the backer board to the floor boards.

sound and settled floor boards can be tiled directly on to un sound and uneven floor boards will possibly require replacement or where needed covering with plywood sheeting this varies in thickness depending on type of floor to be laid ie wet room or utility