Foot function and load is vital to avoiding injury and working out with success. SMR is a great application for general wellness and also nagging pain like plantar fasciitis...something most people who exercise (and even those who do not) will experience are some point or another. Plantar fasciitis is a label the doctors have given pain in the bottom of the foot and/or heel. Often times it may be inflamed from something called the plantar fascia. A very thick, tough connective tissue. It runs across the bottom of your foot and connects your heel bone to your toes. If left untreated it may cause heel spurs and other conditions.
Here's a quick overview of how to apply SMR for the foot. The sole is and calf muscles play a crucial role in ankle mobility and controlling the foot. This is why you also see a calf release.
You will need a tennis ball or a 4 inch inflatable ball. You can do this either sitting or standing. Start by rolling your foot over the ball to find a tender spot. Once you find a tender area sink into the foot with the ball without forcing. Stay in this area for a minimum of 5 minutes or longer. Then, find another area of tight or tenderness and gradually sink into that area for 5 minutes or longer. The key is to never force the tissue into releasing, and stay in the area for the allotted time of 5 minutes or longer. This technique will get into the deeper layers of fascia. Apply the same principles to the calf. It is highly recommended that you also address the calf as the connective tissue/fascia is interconnected. There is more to it than that, but it should get you started.