For just a few slides, it is not worth the investment in a good slide scanner. I've owned both dedicated slide scanners (a Nikon and an Acer) and flatbed photo scanners with slide/negative capability (an Epson) over the last twenty years. The one I am using currently is an Epson Perfection V800 flatbed with the ability to scan slides and negatives up to 8x10". It takes practice and good equipment to get good results.
It was worth my expense and time since I have been scanning family negatives and photos going back over a hundred and fifty years. The oldest negatives date to the early 1900s and we have some glass slides from the 1890s. Many of the negatives are larger than standard medium format negatives so I had to spend more for the larger format transparency capability.
The newer scanners are much better than the older ones in terms of resolution, dust & scratch clean up, and automatic color correction. I need to go back and re-scan many of the ones I did with the older scanners to improve the quality and resolution. Someday in my copious spare time (yeah, right) - there are thousands that need to be re-done.
For just 12 slides, I'd find a service to scan the slides for you - or try the method OxQQme suggests. Do check to see if you can find a service to do it locally - some of the ones send the slides off the India and you may not want to take a chance on that.
You want to scan the negatives at a high resolution - I scan my 35mm slides and film at 3200 dpi. That is high enough to get good quality prints at 8x10" or larger. Any higher dpi picks up more film grain and takes a huge amount more time.