Here is a snapshot I took last night of a friend opening a birthday present. I think that the image is in the vein of what you are trying to capture with the K-5's pop-up flash.
With this image, I set the flash exposure to -.7. I also set the white balance to "cloudy," as this seems to enhance some of the warm colors that are often lost with indoor flash photography. I used a kit lens - 18-55mm WR. Exposure settings were f5.6, 1/100s, and ISO 800. The only thing that you have with this image that you wouldn't with a multi-flash type setup is some minor reflections in the background behind her head. (However, it is a mirror above her head, so how much of that can you really control?)
Hope that helps you out! I'd be happy to take any further suggestions from others - I only started in digital photography a couple months ago. But previously, I shot everything manually with a Canon AE-1 Program.
Last edited by MrJed; 01-14-2014 at 05:02 AM.