I've got an arduino controlled guitar FX loop, which has 4 double relays as part of the circuit. These, along with the arduino, need securing inside a case. I wondered if there is a recommended method of doing this? Some way to arrange and secure them in position? I could fasten them to a thin piece of wood, but it doesn't look very professional.
Are you talking about a project box? Those are widely available - Typically you design the PCB to fit the box, not the other way around.
I've also made my own boxes, and done the mounting-to-a-backing with standoffs thing in several projects (sometimes with a cover over it).
This may give you some ideas (4 methods) :