To make the process faster, warm the almonds in an oven preheated to 350ºF degrees for 10 minutes.
Transfer the almonds to a large food processor fitted with an "S" blade, and process them until creamy. You may want to stop and scrape down the sides every now and then, but this process will take up to 25 minutes. The almonds will first look like a flour with clumps, then will form a ball that moves around the food processor, then it will turn to a grainy almond butter before it becomes silky-smooth. Be patient! Just when you'll want to give up is usually when the magic happens.
Once totally smooth and creamy, transfer the almond butter to a glass jar and store it in the fridge. I've found that almond butter with no additives usually lasts at least a month in the fridge, but be sure to check for signs of spoiling (such as mold or a bad smell) each time you use it.