Step 1: Prepare Your Glasses. Rim your serving glasses with salt if desired. To do this, moisten the rim of each glass with a lime wedge, then invert the glass onto a shallow plate of coarse salt. Gently twist to coat evenly. Set aside.
Step 2: Combine Ingredients in Blender. In a powerful blender, combine the Blanco tequila, fresh lime juice, orange liqueur, and agave nectar.
Step 3: Add Ice. Add about 4 cups of ice to the blender. The amount of ice can vary slightly depending on your blender's power and your desired consistency.
Step 4: Blend to Perfection. Secure the lid and blend on high speed until the mixture is completely smooth and has a thick, slushy consistency. You might need to pause and stir with a tamper or spoon (only when the blender is off!) to ensure all the ice is incorporated and there are no large chunks remaining.
Step 5: Taste and Adjust. Pour a small amount into a spoon and taste. Adjust sweetness or tartness with more agave nectar or lime juice as needed.
Step 6: Serve Immediately. Pour the frozen margarita mixture into your prepared, salt-rimmed glasses. Garnish each with a fresh lime wedge or wheel. Enjoy immediately!