The best place is chidakasha. That is, the space that you see in front of your closed eyes.
Some people say that you should visualize the objects in the hridayakasha, the space in the region of the heart. Others suggest that one should visualize in the daharakasha, the space in the region of the pelvis at the mooladhara chakra. These spaces can be utilized for this practice and any other meditational practice, but most people will find difficulty in perceiving these spaces. For this reason we recommend visualization in chidakasha.
The explanation of this technique is very simple, but the actual practice is a little more
difficult, especially for beginners. The technique is as follows: Take a comfortable sitting position. Close the eyes. Look at the blank space that you see in front of your closed eyes. Think of any object. Try to visualize this object in chidakasha. You may find this difficult; don’t worry. Watch the image for a short time, say up to 30 seconds. The image can be stationary or moving. Then wipe out the image and think of another object. Create a new image. Continue in this manner for as long as you can spare time for the practice.