You can turn pork fat into lard by simmering it slowly to melt it and free it from the tissues that restrain it. The process, called rendering, creates the smooth-textured lard you can purchase in stores for making pie crusts, pastry or for frying. If you render leaf fat only, you can make the highest quality lard, light-colored with a mild flavor. Fatback also makes light, mild lard.
Chop up the pork fat into cubes no larger than 1 inch and place it in a large pot on the stove. Set the temperature on low and let the fat start to melt, stirring it regularly. If you're concerned that it will scorch, you can add a small amount of water, which boils off later.
Raise the temperature slowly to bring the fat to a simmer, being careful not to heat it too quickly and scorch the bottom. Stir it occasionally. As it liquefies, you'll see solid pieces called "cracklings" rise to the top. Allow the lard to continue simmering until the cracklings sink to the bottom, indicating it's ready. You can also test the temperature with a candy thermometer. When it rises above 212 degrees Fahrenheit and approaches 255 F, it's done.
Turn off the heat and allow the pot to cool a little. Set out jars or other heat-proof containers and strain the liquid lard into them through a piece of cheesecloth or a sieve. You can save the cracklings for seasoning beans, if you wish. Seal the containers and place them in a refrigerator or freezer to cool them quickly, to help prevent the lard from acquiring a grainy texture. You can store the rendered lard for several months in the refrigerator or freezer.
Be careful working with the hot fat, which can burn you or catch fire. Watch out for spitting grease as the water evaporates from the simmering fat.
Heat the fat slowly to avoid scorching it. Overheating it also can give it a bad flavor.