Almond flour and almond meal, its coarser counterpart, are made just from almonds skinned and ground fine to be used in cakes, macarons, or meringues. It is time-consuming to make almond meal at home, but since whole almonds can be had for a fraction of the cost of almond flour, sometimes this is worth it.
These instructions include a step for blanching and skinning almonds, which is useful for more purposes than almond meal.
1 pound whole unsalted and unroasted almonds
Preheat the oven to 350ºF. Bring a large pot of water to the boil on the stove and have a colander ready in the sink. When the water boils, tip in the almonds and let them boil for just about a minute. Immediately dump into the colander and run cold water over them.
Let the almonds sit until cool enough to handle, then squirt them out of their skins. Their skins will have loosened and become thin and wrinkly, so this should be easy, not to mention fun.
When the almonds have all been forcibly removed from their jackets, spread them out on a cookie sheet and roast in the oven until they are quite dry. This will take between 10 and and 15 minutes. Watch closely to make sure they don't brown too much, although, depending on the recipe you're intending to use them for, a darker, more roasted taste may be desirable. If you have time to let them sit, turn off the oven and let them sit there all night to dry out even more.
When the almonds are toasted and quite dry, blend them in a food processor. Do not overfill the food processor; it's good to only fill the bowl about half full. Grind in short, quick bursts until the meal is a fine texture. Depending on your food processor and how dry the almonds are, this may not get to the finest flour consistency. If it begins to clump together or turn to butter, it has been over-ground.
This can be stored, tightly sealed, in the freezer for several months.