Those pesky little acorns that drop all over your yard could keep you eating in a survival situation. It's a relatively lengthy process from start to finish but it's well worth it. You can also use this flour at home to make breads, pancakes and other baked goods. Below you find step by step instructions for hot to take an acorn to flour in a primitive situation. In parenthesis I will suggest some faster ways for making this at home.
Step 1 - Collecting: You want to make sure to collect healthy acorns. Check for any holes on the acorns as this equates to worms and you definitely want to stay away from those. Once you have gathered up a good amount of acorns it's time to crack them open.
Step 2 - Crushing: Try to find two rocks that are smooth and flat. If one of the rocks has an indentation on it this will work even better as it will help hold the acorn in place as you crush it. Preferably, you want the nut to come out pretty much in tact. If it's all crumbly when it comes out it probably isn't a good nut to eat. (Crushing acorns at home can be time consuming so you can use a nut cracker to get the job done quicker.)
Step 3 - Grinding: Now it's time to take the nuts you smashed open and grind them down into smaller, more powder like pieces. In the next step you will remove tannins from the nuts and it will be a quicker process if the size of the nuts are smaller. You can do this by just smashing the nuts more with the rocks you used before and grinding them to a powder consistency. (For my home makers it's time to break out that food processor. This will make your life so much easier. Drop your nuts in and grind away.)
Step 4 - Tannin Removal: Acorns have a good amount of tannin in them which can make them bitter. Tannin is what makes a river have a brownish color and comes from plant material leaching into the water. To remove this from the nut you will want to soak them in a flowing river. You can use a sock, t-shirt, cheesecloth or similar material to put the flour in for soaking. The longer the nuts sit in the water the more tannin that leaches out. Certainly leaving them overnight will get the job done. (If your doing this at home and don't have access to a river you can soak the acorn powder in the sink. Fill the sink and let the acorns sit for 30 minutes to an hour. Drain the water and repeat the process a couple more times.)
Step 5 - Drying: Place the nut flour out in the sun to dry. The timing for this process will depend on the amount of flour and how sunny it is. Once you have dry flour you can store it and use it as needed. In a survival situation you can mix the flour with water and eat it as a paste.