• If it's your first time rendering tallow, start with the slow cooker method below--it's a gauranteed no-fail way to  learn the process of rendering without the chance of scorching the tallow.
• Chill the fat. Using a chef’s knife cut the fat into small cube-sized pieces, about 1x1 inch. Put the lamb fat and water into a slow cooker, and cook on low heat for 8 hours, or until the fat has rendered and looks clear, stirring occasionally.
• The chunks of lamb fat should not brown too much, and it’s better to cook the fat a little less than to over cook it which can give it a toasted flavor that, while not the end of the world, is not properly rendered tallow. When the fat is rendered, allow it to cool for 30 minutes to an hour before straining, as it’s very hot.
• Strain or fish out the cracklings and reserve. Pour the fat into glass jars while still pourable, but don’t seal them until cool. When cooled, the tallow should be pure white. Store one jar of tallow at room temperature to make it easier to spoon out and portion, and freeze or refrigerate the rest. The tallow will last a very long time under refrigeration or in the freezer.

To make cracklings from the leftover fat

• To make cracklings from the leftover fat, put the cooked, still white pieces of fat into a heavy cast iron pan (12 inch diameter) or similar, and bake for one hour at 300, or until the pieces of fat are crisp and browned. You can drain off the additional fat that comes out of the cracklings for cooking.