Cut the grass-fed fat into small cubes. Put in shallow pan with a small amount of water to prevent burning until the fat starts to melt. I start my oven at 325 until there is a good amount of melted fat to cover the bottom of the pan, then turn it down to 300. Check every 30-60 minutes, stir. After an hour or so the water will have cooked out and you can start to pour off the lard as needed. I strain it through a metal strainer into glass jars and refrigerate.
As you near the end of the rendering, you get cracklins. I usually turn the oven down to 275 and let them crisp for a few more hours, stir as needed. You can make them as crunchy as you like. Add lots of salt or other seasonings. I keep mine in the freezer and reheat as needed.
The lard will be yellow until it cools down and solidifies. Keeps for months in the fridge. It is delicious.