Soaking your feet in a solution of boric acid is sometimes recommended for cracked heels, but this is not the ideal solution. The reason is that cracked heels are always also dry, as you have mentioned - in fact the main cause of cracked heels (or heel fissures, as they are sometimes known) is severe dry skin. This is something that boric acid will not address, and in fact, it might exacerbate the problem of dryness.
Other factors that can cause cracked heels include standing for long periods of time and wearing shoes that are open at the back. Being overweight can also contribute to the problem, as it increases the amount of pressure that is put on the heels. It is however almost always the case that the dryness of the skin is the most important factor, and is the one that makes it possible for these other factors to have an effect. In order to remedy cracked heels therefore, you need to address the problem of dry skin. The best approach is to bathe before going to head (or at least soak your feet for five minutes, in plain water), pat them dry, and then immediately apply a thick moisturizing cream. You can also apply aloe gel to your feet a couple of times during the day.
Although dryness is the most important factor, it is also necessary to identify and address the other factors that may be causing the cracked heels. See if you need to lose weight, try wearing closed shoes as much as possible, and avoid spending too much time at a stretch on your feet.
If the cracks are very severe, and if they are accompanied by tough calluses, it is advisable to first visit a podiatrist; after a session or two, you can take care of your feet on your own.
answered by M W