I just purchased a 2007 Econoline E350 XLT and I was wondering what owners do for the flooring when all of the seats are out? I'd like to have some sort of flooring system to account for the seat brackets in the floor. I'll mainly be using this van for hauling, and don't want to have to maneuver around those brackets.

 

Welcome to the site..

I’d probably craft some ply around and/or top of all the brackets. Ply also works well to keep cargo from easily sliding, fairly inexpensive and the surface holds up decently to slide in loading if that applies..
Other surface materials, rubber/vinyl, sheet steel can also be attached to the ply if needed..