In which you leave the work alone, though you still ponder about it occasionally, leaving it ‘on the surface of your mind’.
Many brilliant ideas have occurred in the bath, or in traffic jams. If you are able to stop work on a project for a few days, perhaps to work on other things, this will give your subconscious time to work on any problems encountered, it will also distance you somewhat from your ideas so that you are better able to evaluate them.
‘Incubation’ is particularly useful after an ‘inspiration’ or a ‘perspiration’ phase, or if a problem has been encountered. Creative people are often surprisingly patient and untidy, and are content to let half-baked ideas, loose ends and inconsistencies brew away in their sub-conscious until ‘something turns up’.
Whenever Sir Isaac Newton had a particularly thorny problem he always worked on it just before he went to sleep. He said “I invariably woke up with the solution”.
In order to leave work for your sub-conscious to work on you need to be:
That is you must expect difficulties, trust yourself to find a way round them, and not be panicked into adopting a weak solution. Few people realise that some ideas take time to hatch, and see difficulties and indecision as a sign of failure.
Here is a video of the comedic genius John Cleese describing his creative process. Note how large incubation features in his way of working.