As a new user, I am surprised that the desktop computer player is full of advertising, initially cannot tell if it is on the live TV.
This is totally inappropriate on premium cost device and reflects badly on Sling making their user experience second class for a small increase in revenue.
I was unaware that there is no built in method of Chromecasting from Singplayer desktop to a TV and find that the Sling support pageboys it is not possible.
I have Cast a connection from Google chrome and used the option to cast the whole computer screen, I have then opened Slingplayer and used the full screen option.
Hardly rocket science.
Retrieving data ...