There are two ways to save a slide to a flash drive. The first way is to export the slide as a PDF. To do this, open the slide in PowerPoint and click on File > Export > Create PDF/XPS Document. In the Save As dialog box, choose where you want to save the file and click Save.
The second way to save a slide to a flash drive is to take a screenshot of it. To do this, press the Print Screen button on your keyboard. This will take a picture of your screen and copy it to your clipboard. Then, open up Paint or another image editing program and paste the image from your clipboard. From here, you can crop out just the part of the image that contains your slide and then save it as a JPEG or other image file format onto your flash drive.