The answer to the above questions can be explained in the steps below:
1. Looked for some leftovers of any of your new cardboard or cardstock stencils. Most of these stencils come with their stenciling area pre-cut but not removed yet. We would normally removed these pieces and throw it away before stenciling. Now with this technique, you would want to save all those pieces up.
2. Put some adhesives or liquid glue behind those pieces before removing them directly to your layout.
3. Put it directly on your layout and using a pencil or tweezer, slowly give a little push on those pieces and secure them down on the layout. This will ease the placing process.
4. Lastly, use some ink, gel pens, paint markers or any art materials you want to decorate it and give some details to eat. You can even tailored your colour on it to match your layout.
This technique actually give a more dimensional look to the layout and placing it anywhere in the layout is possible unlike stenciling.
Just another tip, you can also use these pieces as masks. So next time if you come across these cheap cardboard stencils, think twice before you throw any pieces away.