My fiancé and cousin are laying vinyl hardwood planks in my foyer. The entry part near the door is slab and carpet has been removed from the other part. They had to lay 1/4" wafer board to even that part of the floor with the slab. They started to lay the planks (which do have adhesive tabs around the edge) against the wall edge of the slab and wafer board, but the planks are not adhering to the floor. Should they prep the slab and board with a primer and/or sealer and adhesive before they lay the planks?