These joints are the simplest of all edge joints. Their primary purpose is to produce wood stock that is thicker than can be economically purchased by gluing together two or more flat boards.
The key to successful face-to-face joints is to have the surfaces flat and clean. When the two pieces are glued together, any voids between the pieces may be visible at the edge, and will reduce the effectiveness of the glue holding them together.
An important precaution to note is that attempting face-to-face joints with different wood species is a recipe for disaster, and should only be attempted when attaching a thin layer to a heavy/stable layer. An example would be to apply a veneer to a plywood base. This is because the different species of wood will expand and contract at different rates, and will cause the wood to warp or ripple.
No mechanical fasteners or fancy joints are required for a successful face-to-face joint.