While I was working as a Media Applications Coordinator, I designed webcasts almost every day. You can see more information about this on my resume. The following is an example of what those webcasts looked like. First I made a landing page using the client's graphics and design scheme to personalize it.

Then there was a page where the webcast was streamed. These typically included interactive slides on one side and then an audio or video player on the other.

Webcast Samples:

Citizens Financial Group
Five Below Inc.
The Home Depot, Inc.