- Cook a batch of something and dehydrate it 'whole'
- Dehydrate ingredients and the mix them together to make up the recipe
Both work well. The choice of which to use is really down to the style of food.
Obviously for things like curry and stews then you need to use method 1, the cooking times required are completely impractical when camping.
Method 2 works well with quick-cook items such as porridge or noodles.
You can combine both these methods into your normal shopping / cooking routines; make extra portions of long-cooked items and dehydrate and store in the freezer, pick up seasonal items and/or special offers and dehydrate them, store in freezer and then use to make up portion packs. (I recently bought a load of spring onions and courgettes, sliced / julienned them and stored them to use in versions of the chinese noodles recipe. I also did apples for porridge)
Without major effort you can build up a 'bank' of dehydrated meals with a fantastic selection of recipes. This will easily outshine any commercial range for choice and quality as well as being far, far cheaper.