1 hr easy ride with a few 5 minutes intervals at ftp to open the legs up for the next day. Probably pretty similar to Jonathans pick as sometimes I like to ramp it up a bit towards the end of the interval.
As a side note, I have missed the opportunity to do a leg opener the day prior to an A race and I felt terrible in the event. Not sure if it was entirely due to missing a session but I do think it impacted me.