Go to Google Slides (you have to have a google account for this obvs.)
Click on the not at all obvious coloured plus on the bottom right and make your slides
When done, go to File > Publish to the Web > Embed tab (select the size you want), then Publish. Then copy the embed code that appears.
In your Canvas page, go to Insert/edit Media at the top of the Rich Text Editor and in the Embed tab, paste in your embed code.

My embed code looked like this:

If you want you can go to HTML Editor and change the highlighted number to 90% so that the embedded viewer autofits to 90% of the page width.

And here is the final embedded Google slideshow: