Setting Samesite Attribute in Persistence Cookie

I watched the "Lightboard Lessons: HTTP Cookie SameSite Attribute" by JRahm and in that video he mentions that an iRule or local traffic policies can be used to set this attribute.  I have the iRule and it seems to working, but I wanted to know how I would create a local traffic policy to set this attribute.  I am doing this on LTM's that are running version 15.1.5.1 Build 0.0.14 Point Release 1.