I am yet to meet a person with absolutely no ability to hold a mental picture, however vague that picture may be at first attempt. Teenage boys tend to have reasonably good ability in this area, for obvious reasons, but there is still work to be done. Your average fantasy does not have much by way of fine detail. To perform this exercise you will need an analogue clock or watch.
Begin by completing the breathing exercise. By now, you should be able to do this start to finish very quickly. You should next attain the blank-mind state, either by performing that exercise in its entirety or by simply shifting to that state if you are able to do so. By now you should find that simply beginning the breathing exercise will get you on the right track, and you will be mentally calm and ready to begin the exercise. This sort of practise turns a short breathing exercise into a quick preparation for work that lasts only a few moments, but which prepares you adequately for mental work.
Pick up the clock and take a really good look at it. Notice the format the numbers are in. Are they in our standard hindu-arabic style, or are they roman numerals? Are the spaces between the numbers incremented, or are they simply blank? What do the hands look like? Does the second hand move once per second, or does it make a continuous, slow progression around the clock face? Really focus on all the details, paying specific attention to each feature you notice. When you feel you are ready, put the clock down and close your eyes.
Create a mental image of the clock. This is very easy, until you attempt to fill in all the fine details. You may find that you can get a good overall image, but the details are a bit vague. Perhaps you can create detail in one area, but at the loss of the remainder of the image. It is quite common to be able to fill in details only if you are focusing on one area only, as though you are in a “close-up” view. This is normal. I’ve found that while it may be difficult to visualise something complex, I search my memory for the image and find that it is there. You may find it helpful to imagine the clock as you were holding it. Try to let your mind fill in the blanks rather than struggling to hold it all at once and push further detail in. You may have noticed that each exercise places emphasis on allowing things to happen, to guiding one’s mind rather than forcing it. This holds true with all mental pusuits. You’ll find that your mind is a willing accomplice in all endeavours, so long as you approach the issue with the right attitude. See how much detail you can put into the image, and then open your eyes and look at the clock again. Did you miss anything? Was there anything that wasn’t quite right? How much did you get right the first time? It’s surprising how many small details are in an object as simple as a wall-clock. Once you’ve reviewed to your satisfaction, close your eyes and return to the mental image.
Repeat the exercise frequently until you are happy with your ability to visualise the clock, then add the element of movement. Start by having the second hand move, and see if you can make one complete revolution without breaking focus. Once you can do that, complete multiple revolutions, ensuring you don’t forget to have the minute hand move with each revolution.