I do want to note that I use a dehydrator and a grain mill when I make mine, but it is also possible to make sprouted flour using your oven and a good-quality blender. There is more risk of over-cooking the grains (or even burning them) in the oven, but if you're careful, this shouldn't be a problem. A blender may not grind all of your grains perfectly evenly, and you can only do very small batches, but it does work in a pinch. So don't let a lack of equipment stop you from trying.
The first thing you need is whole grains - wheat "berries", rye, spelt, oats - pretty much any seed you'd make flour with will germinate this way (this is also a good preparation method for beans; just cook them after they've sprouted and skip the dehydration and grinding steps). I do want to note that this doesn't work well for flax - the grains make a slimy coating when they're soaked, and they should never be run through a grain mill because of their high oil content. It also won't work with oatmeal, because once the seeds are rolled they can no longer germinate.
The way I like to do it is to fill a wide-mouth quart jar with about a cup of grain (size of the jar doesn't really matter - just big enough for the amount you're working with, and able to be covered for the draining step), then cover the seeds with about an inch of water (the grains will swell as they soak. If the grains get above the water during the soaking stage, just add more water). Warmer water will help the process along. Hot tap water is fine - just not too hot, you don't want to cook the grains (but your tap water shouldn't be that hot anyway!) Set them on the counter to soak for 8-12 hours.
As a side note, the sprouting water than you drain off is great for plants, and some people even drink it as a health tonic (I'm not one of those people - I give it to the plants). I use a funnel and store it in an old gallon milk jug, then use it to water my houseplants.
I like to dry my sprouts at about 105 degrees F in my Excalibur dehydrator (I love that it has adjustable temperature settings), to preserve as many nutrients as possible, but if you're dehydrating in an oven, just use the lowest temperature you can (you will be baking these grains, after all, so don't stress too much about the temperature here - but you don't want to bake them before you put them in the final product, either). I leave them in the dehydrator for around 4-6 hours, or until a seed from the dehydrator "crunches" the same in my teeth as a seed fresh out of the bag (very scientific, I know!)
When the seeds are properly dried, you can then either store them whole in the refrigerator, or grind them and then store them. I prefer to store them in the refrigerator because the oils in whole grains can go rancid quite quickly (another reason to grind your own flour and never buy unsprouted/non-sourdough whole grain products from a store!) I love sprouted flour for baking - I can use it just like I would any store-bought flour, and it actually gives a lighter, fluffier texture than unsprouted whole grain flours. I use it mainly for cookies, quick breads, and such, but sprouted wheat bread is also a favorite treat (when I don't have time to wait for sourdough but I have sprouted flour on hand).
