I went through 2 coffee grinders and countless hours testing different types of almonds and methods and finally settled on the method described here. Not only is it much cheaper but its very easy to do.
What you'll need:
Food processor (I have a Ninja branded unit)
I found almond slivers in bulk at a local market, Winco. They have a 'bin' section with all sorts of stuff good for gluten free diets. Nuts, unsweetened dried coconut etc.
I tried raw almonds and sliced almonds, but these still have the brown husk on the almonds. It works, but your flour comes out brownish.
1: Put almonds in the processor.
2: run for a minute or 2.
The final product is not as 'refined' as the store bought stuff, but I have tried it in many recipes from cookies to meatloaf and it works great!
I read many warnings about over-grinding almonds and it turns into butter. I haven't had this problem despite running the grinder for 5 minutes. I get some clumps but they break up pretty easy.
I store the flour in my refrigerator.