I'd either put them on ahead of the FC or after the planter.  

Honestly, I prefer after the planter for pre's if you can count on rain to get it activated.     After the planter means you get an undisturbed blanket of chemical over the entire field, no streaking from tires or row cleaners.

Only twice in my years of farming have we been bitten (several weeks without any real rain) by laying chemical on top of the ground after the planter, those 2 years were 2022 and 2023.    I'm hoping not to have a threepeat, so far this spring is acting more like a normal spring with normal spring rains.