Pour 1 cup of bone broth, broth, or stock into each of your (1) shallow baking dishes or (2) homemade baking dishes that you placed on a baking sheet. (See video to learn how to create a homemade baking dish from parchment paper.)
Place baking sheets with baking dishes into a pre-heated oven at the oven's lowest possible temperature setting. The oven temperature should be somewhere between 150°F and 200°F.
Allow bone broth, broth, or stock to dry until crisp. This will take approximately 8 hours if your oven temperature is set at 170°F. (The drying process time will be longer or shorter if your oven is set lower or higher than the mid-range 170°F.)
Rotate the baking sheets halfway through the drying time.
Once the bone broth, broth, or stock has dried to a crisp texture, transfer it to a grinder or blender and pulverize until it is a fine powder. This is your bouillon powder.
Transfer the bouillon powder to a jar with a lid. Make sure that it is completely dehydrated and VERY dry. Preferably, add a food safe oxygen absorber plus a food safe silica gel pack to the jar to extend its shelf life. (PLEASE SEE IMPORTANT RECIPE NOTES BELOW.) Store in a pantry or cupboard out of direct sunlight, or to extend the shelf life store in the refrigerator or freezer. As with all homemade items, it can be difficult to determine exact shelf lives. If you detect an unpleasant odor or mold at any time, discard immediately.
Optionally, you may add equal amounts of salt to your bouillon powder to create a product that's similar to commercially manufactured bouillon crystals or bouillon cubes. (For example, if you have one cup of dehydrated broth, you would add one cup of salt to make a two cup mixture that would have a similar consistency to store-bought bouillon.)
As an extra step to extend your bouillon powder's shelf life, you can use a handheld Foodsaver to extract as much oxygen out of your jar as possible. (See video for how to use the Foodsaver.)
Alternatively, you can refrigerate or freeze your bouillon powder. It will not change the taste or texture.