Can I use the whiteboard in this way? Then have it disappear once I arrive and start teaching? Than

This could certainly be accomplished with the new Zoom Whiteboard or just sharing your screen in combination with a Powerpoint or Google Slides presentation. Either way would work, just depends on how much design you want to incorporate in the notice. If going for more complicated, I'd go with the slideshow. 

Hope that helps and please make sure to mark the solution as accepted if this information is what you needed.

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