Step 1: Ingredients
A food dehydrator(or an oven that can be set very low)
Optional: Honey (raw is best but store bought will do)
Apple chips (home made is best, but again, store bought will do)
Step 2: Put It Together
And if you choose to add honey or apple chips you may alter as you wish but a good starting point is 5 parts flour/sauce mixture to 1 part honey or apple chips (be sure the chips are broken up into somewhat small pieces)
Once you have the dough made (it should be about the consistency of cookie dough, though a little bit stickier) you can flatten it out on a pan to put into the dehydrator. If you go that route you simply cut it into squares once it is dry. That is easy enough, but I prefer to dry it in smaller pieces so that it will dry quicker. I like to use plastic baby food lids since I have a lot of them and then they are a good uniform size.
The drying time will vary a little bit based on your dehydrator temperature; also adding honey makes it take longer as well. But in mine it usually takes about 10 to 12 hours, going about 6 to 8 hours on the first side and flipping it over (taking it out of the mold to do so) to dry the underside for about 4 more hours. You will know when it is sufficiently dry because it will no longer be sticky and it will be uniformly a much lighter color. If it is sticky anywhere or has dark patches anywhere then it's not done drying yet.
Step 3: How It Works
The next improvement is using applesauce instead of water; you need some kind of liquid to make the flour into a paste for forming it into bisquits and applesauce will do the trick while adding nutrients as well as keeping the mixture soft even when it's dry. I have been able to successfully preserve apples through dehydration so that they last for at least a couple of years, as long as the moisture is all removed then the applesauce will keep for a good while.
Another improvement is adding honey if you choose to. Honey has been found in ancient tombs and was not only still edible but actually nutritious! Adding honey will help preserve the bisquits and make them taste better, though they don't seem to make a difference in how hard/soft they turn out.
Lastly, they are dehydrated, not baked. This is a subtle but important difference. Since it never gets hot enough to actually bake it, the ingredients retain many of the same qualities of being raw. The most important of which is that the nutrients in the oats don't brake down as much so this recipe is quite a bit healthier than normal hardtack. Dehydration is also more effective at removing moisture (although it is slower), which is very important since applesauce is definitely perishable if it's not totally dry.
And that's about it! So far I have had very good luck with these storing well as long as they are kept dry. They are much more edible than standard hardtack, I even give them to my 1 year old- that's how much softer and better tasting they are. Now don't get me wrong; these still aren't that tasty, but in a survival situation I would much rather have a pack full of these than those bricks they call food.
I hope this has been helpful and that it comes in handy for somebody some day!