How do you "cast off in pattern"?

I am working on a poncho that simply repeats two mildly different rows. I have reached the required length for the front piece and the pattern states “Cast off in patt.” My pattern is basically a k3, p1, but the two rows differed in how they started and ended. Should my cast off follow the pattern of the first or second row? I’m confused.

Follow the row you would be making as if you were following the pattern, but cast off.

I’m just a beginner myself, but I would knit row 1 of the pattern, then cast off in row 2 of the pattern. This will then finish the project with a completed pattern.

Thanks for your help. I just realized that there is a video for casting off in pattern–I didn’t scroll down far enough on the page. Oh well.