How can I put a Google map into a slide?

Go to Google maps, and look for the address you want to show.
Then click on the little gear icon in the bottom right, and click on Share and embed map
Choose Embed map and copy the iframe code.
It will be something like this:

<iframe src="!1m14!1m8!1m3!1d2686.201067203608!2d17.6327019!3d47.680515!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x476bbff067c5bc01%3A0x5614666fbf541a35!2zS8OhbHbDoXJpYSB1LiAxLCBHecWRciwgOTAyNA!5e0!3m2!1sen!2shu!4v1415616034067" width="600" height="450" frameborder="0" style="border:0"></iframe>

And what you need from here is the link of the src:!1m14!1m8!1m3!1d2686.201067203608!2d17.6327019!3d47.680515!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x476bbff067c5bc01%3A0x5614666fbf541a35!2zS8OhbHbDoXJpYSB1LiAxLCBHecWRciwgOTAyNA!5e0!3m2!1sen!2shu!4v1415616034067

Put down an iframe item into your slide, paste this link into the iframe url, and you are done. In the slide editor it might look smaller, but in the frontend it will have 100% width and height.