PowerPoint has a feature which allows you to remove the background from an image. There are limitations such as needing a high-resolution, decent quality image and a clearly defined background/foreground, It still has many uses and can allow you to bypass the need for you to search for a 'cut-out' stock image to start with.
Inserting an Image
The first step to remove the background of an image is to insert the image you wish to remove the background from. If you are not sure how to add an image to your PowerPoint, there is a guide here.
Remove the background
Once your image has been added to the PowerPoint, select it with a left-click. You can tell the image is selected because you will be able to see the 'resize-handles' (little white circles) on the edges of the image used for resizing it:
Once the image is selected, select the 'picture tools - format' found in the middle of the ribbon, you will only be to see this if the image is selected. Once in this menu, select 'Remove background':
Now that the 'remove background' button has been enabled, PowerPoint (or the other Microsoft Office apps) will automatically try to guess what is the foreground and what is the background. Anything coloured in purple will be removed from the image when the 'keep changes' button is clicked:
However, if PowerPoint does not suggest the correct parts of the image to remove (which it likely won't without some manual input) you can use the "Mark areas to the keep" and "Mark areas to remove" buttons to draw over the image and change what PowerPoint will remove/leave:
Once you are happy with the layout of the image, click "Keep changes" in order to finish and remove the part of the image highlighted with purple.