Usually when asked to produce a radio commercial that is not just an announcer extolling the virtues of a product, I am sent a script that gives some indication of where the action takes place. This needs SFX to paint the picture. For instance, at the races (horses hooves, crowds etc), in a park (rustling leaves, ducks splashing in the pond and quacking, birds chirping, ambient outside noise). The sounds in the background will place the listeners subconsciously wherever you want them to be.
Occasionally one has to stretch the imagination. One client asked me to place the idea of his radio commercial as a silent movie with Charlie Chaplin. A use of some old fashioned piano music and a whirring projector was the best I could come up with. Another asked me to 'start commercial with couple sleeping peacefully on their comfy new mattress' (I suggested a light snoring noise but this was rejected!).
But last week I was completely beat. A client in Russia asked me if I would produce a commercial for him. I asked him to send me the script which he said was for a new seafood restaurant. When it arrived it appeared that a woman was to have a conversation with a lobster. There was no dialogue for the lobster (actually I have performed as a lobster for a computer game using some very odd clicking noises) and the woman did not mention lobster other than by a name when she spoke. I tried to explain that this was a tableau that I was not able to construct, but he was having none of it and didn't appear to have any ideas of his own. We parted amicably with him saying he would get someone local to produce his commercial! Oh well....onwards and upwards.