I should know this - casting on only 1 st

I’m starting my first shawl (the Candle Flame Shawl) and it starts with “CO 1 sts”. Simple right? Not really. Do I just do a sl st and go from there? Anything else that would be easy/easier?

I’m just completely drawing a blank about this and feel silly…

Yeah, do a slip knot, then k, YO, K into it.