Flat ground, 4m log beams in zig-zag pattern causes short leg mobs to path differently. If you want, leave a gap with a killing area, or just run out, hop over, hop back. Against trolls this does not do anything. Fulings is good.
For trolls the key is gaps, the moat makes them stand back or sometimes fall in which is good, but if doing a wall, you need to account for the long reach of log trolls. So a gap between outer and inner is what is needed.
If you are running out to kill the things then anything will do.